[EC2] Cosmetic fix for usage of spark-ec2 --ebs-vol-num option
[EC2] Cosmetic fix for usage of spark-ec2 --ebs-vol-num option

The last line of the usage seems ugly.

```
$ spark-ec2 --help
<snip>
  --ebs-vol-num=EBS_VOL_NUM
                        Number of EBS volumes to attach to each node as
                        /vol[x]. The volumes will be deleted when the
                        instances terminate. Only possible on EBS-backed AMIs.
                        EBS volumes are only attached if --ebs-vol-size >
                        0.Only support up to 8 EBS volumes.
```

After applying this patch:

```
$ spark-ec2 --help
<snip>
  --ebs-vol-num=EBS_VOL_NUM
                        Number of EBS volumes to attach to each node as
                        /vol[x]. The volumes will be deleted when the
                        instances terminate. Only possible on EBS-backed AMIs.
                        EBS volumes are only attached if --ebs-vol-size > 0.
                        Only support up to 8 EBS volumes.
```

As this is a trivial thing I didn't create JIRA for this.

Author: Kenichi Maehashi <webmaster@kenichimaehashi.com>

Closes #7632 from kmaehashi/spark-ec2-cosmetic-fix and squashes the following commits:

526c118 [Kenichi Maehashi] cosmetic fix for spark-ec2 --ebs-vol-num option usage

rekhajoshm/spark,patrick-nicholson/spark,kiszk/spark,apache-spark-on-k8s/spark,stanzhai/spark,kimoonkim/spark,esi-mineset/spark,szhem/spark,liyichao/spark,Aegeaner/spark,gengliangwang/spark,gengliangwang/spark,facaiy/spark,janewangfb/spark,debugger87/spark,adrian-ionescu/apache-spark,darionyaphet/spark,pronix/spark,setjet/spark,chuckchen/spark,ahnqirage/spark,JerryLead/spark,darionyaphet/spark,WeichenXu123/spark,haowu80s/spark,byakuinss/spark,dbtsai/spark,milliman/spark,jiangxb1987/spark,kiszk/spark,sahilTakiar/spark,loneknightpy/spark,jrshust/spark,markhamstra/spark,UndeadBaneGitHub/spark,pronix/spark,minixalpha/spark,actuaryzhang/spark,ajaysaini725/spark,mzl9039/spark,cloud-fan/spark,minixalpha/spark,chuckchen/spark,aosagie/spark,JerryLead/spark,vinodkc/spark,shuangshuangwang/spark,jrshust/spark,skonto/spark,rekhajoshm/spark,xflin/spark,aokolnychyi/spark,darionyaphet/spark,techaddict/spark,gioenn/xSpark,jianran/spark,shuangshuangwang/spark,cloud-fan/spark,rezasafi/spark,shubhamchopra/spark,icexelloss/spark,ddna1021/spark,guoxiaolongzte/spark,gengliangwang/spark,aosagie/spark,jrshust/spark,tejasapatil/spark,jkbradley/spark,1haodian/spark,SHASHANKB/spark,kissmetrics/spark,zero323/spark,saltstar/spark,michalsenkyr/spark,JoshRosen/spark,pronix/spark,ueshin/apache-spark,skonto/spark,saturday-shi/spark,stanzhai/spark,techaddict/spark,skonto/spark,JerryLead/spark,goldmedal/spark,hvanhovell/spark,gengliangwang/spark,panfengfeng/spark,techaddict/spark,ericvandenbergfb/spark,cin/spark,lvdongr/spark,poffuomo/spark,brad-kaiser/spark,bdrillard/spark,sureshthalamati/spark,kiszk/spark,metamx/spark,pronix/spark,bOOm-X/spark,ioana-delaney/spark,byakuinss/spark,map222/spark,mahak/spark,szhem/spark,guoxiaolongzte/spark,ioana-delaney/spark,hhbyyh/spark,aosagie/spark,WeichenXu123/spark,spark-test/spark,rikima/spark,mzl9039/spark,dongjoon-hyun/spark,tengpeng/spark,vinodkc/spark,tengpeng/spark,wangyum/spark,huang1900/spark,UndeadBaneGitHub/spark,bOOm-X/spark,bdrillard/spark,pgandhi999/spark,cloud-fan/spark,ConeyLiu/spark,hvanhovell/spark,MLnick/spark,jianran/spark,cloud-fan/spark,markhamstra/spark,taroplus/spark,haowu80s/spark,gioenn/xSpark,dongjoon-hyun/spark,ron8hu/spark,zzcclp/spark,hhbyyh/spark,patrick-nicholson/spark,JoshRosen/spark,rednaxelafx/apache-spark,metamx/spark,ddna1021/spark,alunarbeach/spark,aray/spark,aosagie/spark,michalsenkyr/spark,saltstar/spark,ibm-research-ireland/sparkoscope,srowen/spark,1haodian/spark,andrewor14/spark,SnappyDataInc/spark,apache/spark,ueshin/apache-spark,nilsgrabbert/spark,setjet/spark,stanzhai/spark,yanboliang/spark,panfengfeng/spark,liutang123/spark,tengpeng/spark,esi-mineset/spark,holdenk/spark,wangyum/spark,zzcclp/spark,rikima/spark,darionyaphet/spark,mzl9039/spark,witgo/spark,hhbyyh/spark,esi-mineset/spark,joseph-torres/spark,saltstar/spark,big-pegasus/spark,bOOm-X/spark,1haodian/spark,joseph-torres/spark,poffuomo/spark,LantaoJin/spark,panfengfeng/spark,WeichenXu123/spark,mahak/spark,SHASHANKB/spark,yanboliang/spark,kimoonkim/spark,lvdongr/spark,sachintyagi22/spark,jkbradley/spark,ptkool/spark,bOOm-X/spark,kissmetrics/spark,wzhfy/spark,ioana-delaney/spark,Panos-Bletsos/spark-cost-model-optimizer,darionyaphet/spark,holdenk/spark,gioenn/xSpark,BryanCutler/spark,vinodkc/spark,nilsgrabbert/spark,eyalfa/spark,rednaxelafx/apache-spark,rikima/spark,hhbyyh/spark,jianran/spark,ericvandenbergfb/spark,shuangshuangwang/spark,poffuomo/spark,szhem/spark,nlalevee/spark,ibm-research-ireland/sparkoscope,big-pegasus/spark,caneGuy/spark,sureshthalamati/spark,ioana-delaney/spark,taroplus/spark,poffuomo/spark,zero323/spark,JoshRosen/spark,tejasapatil/spark,apache-spark-on-k8s/spark,lvdongr/spark,eyalfa/spark,Panos-Bletsos/spark-cost-model-optimizer,debugger87/spark,janewangfb/spark,mike0sv/spark,JoshRosen/spark,mahak/spark,wangyum/spark,cin/spark,publicRoman/spark,setjet/spark,szhem/spark,someorz/spark,lxsmnv/spark,witgo/spark,patrick-nicholson/spark,dbtsai/spark,someorz/spark,LantaoJin/spark,highfei2011/spark,BryanCutler/spark,aokolnychyi/spark,jrshust/spark,poffuomo/spark,MLnick/spark,wzhfy/spark,hvanhovell/spark,publicRoman/spark,icexelloss/spark,dbtsai/spark,JerryLead/spark,ajaysaini725/spark,LantaoJin/spark,dongjoon-hyun/spark,michalsenkyr/spark,loneknightpy/spark,jiangxb1987/spark,alunarbeach/spark,srowen/spark,WindCanDie/spark,wzhfy/spark,mike0sv/spark,debugger87/spark,Aegeaner/spark,shaneknapp/spark,sachintyagi22/spark,BryanCutler/spark,andrewor14/spark,liutang123/spark,sureshthalamati/spark,ueshin/apache-spark,patrick-nicholson/spark,sureshthalamati/spark,witgo/spark,shubhamchopra/spark,darionyaphet/spark,pronix/spark,ptkool/spark,map222/spark,maropu/spark,adrian-ionescu/apache-spark,eyalfa/spark,guoxiaolongzte/spark,spark-test/spark,pgandhi999/spark,dongjoon-hyun/spark,setjet/spark,skonto/spark,jlopezmalla/spark,chuckchen/spark,maropu/spark,brad-kaiser/spark,debugger87/spark,jianran/spark,facaiy/spark,highfei2011/spark,maropu/spark,apache-spark-on-k8s/spark,saturday-shi/spark,jlopezmalla/spark,cin/spark,bravo-zhang/spark,tengpeng/spark,esi-mineset/spark,rednaxelafx/apache-spark,ahnqirage/spark,saturday-shi/spark,bdrillard/spark,shuangshuangwang/spark,jiangxb1987/spark,liyichao/spark,zhouyejoe/spark,WindCanDie/spark,minixalpha/spark,apache/spark,caneGuy/spark,wangmiao1981/spark,brad-kaiser/spark,byakuinss/spark,LantaoJin/spark,ericvandenbergfb/spark,sahilTakiar/spark,mike0sv/spark,SHASHANKB/spark,zero323/spark,WindCanDie/spark,vinodkc/spark,BryanCutler/spark,Aegeaner/spark,goldmedal/spark,SnappyDataInc/spark,michalsenkyr/spark,someorz/spark,1haodian/spark,ConeyLiu/spark,adrian-ionescu/apache-spark,lxsmnv/spark,mike0sv/spark,rekhajoshm/spark,lvdongr/spark,wangmiao1981/spark,dhruve/spark,ptkool/spark,ron8hu/spark,bdrillard/spark,shubhamchopra/spark,zzcclp/spark,jlopezmalla/spark,pgandhi999/spark,jlopezmalla/spark,SHASHANKB/spark,xflin/spark,icexelloss/spark,panfengfeng/spark,WindCanDie/spark,ericvandenbergfb/spark,metamx/spark,big-pegasus/spark,jkbradley/spark,jiangxb1987/spark,kiszk/spark,big-pegasus/spark,eyalfa/spark,shubhamchopra/spark,joseph-torres/spark,huang1900/spark,xuanyuanking/spark,apache-spark-on-k8s/spark,LantaoJin/spark,kimoonkim/spark,wangyum/spark,debugger87/spark,SnappyDataInc/spark,WeichenXu123/spark,andrewor14/spark,panfengfeng/spark,spark-test/spark,bravo-zhang/spark,brad-kaiser/spark,zero323/spark,zero323/spark,ron8hu/spark,goldmedal/spark,aray/spark,facaiy/spark,srowen/spark,minixalpha/spark,debugger87/spark,guoxiaolongzte/spark,1haodian/spark,ddna1021/spark,zuotingbing/spark,jkbradley/spark,rezasafi/spark,sachintyagi22/spark,mzl9039/spark,akopich/spark,witgo/spark,jkbradley/spark,saltstar/spark,liyichao/spark,zuotingbing/spark,wzhfy/spark,ddna1021/spark,liyichao/spark,szhem/spark,rezasafi/spark,someorz/spark,ibm-research-ireland/sparkoscope,aray/spark,rednaxelafx/apache-spark,Panos-Bletsos/spark-cost-model-optimizer,milliman/spark,michalsenkyr/spark,jiangxb1987/spark,techaddict/spark,ericvandenbergfb/spark,gioenn/xSpark,taroplus/spark,ajaysaini725/spark,adrian-ionescu/apache-spark,techaddict/spark,cloud-fan/spark,jiangxb1987/spark,saltstar/spark,jlopezmalla/spark,loneknightpy/spark,guoxiaolongzte/spark,jianran/spark,kimoonkim/spark,lxsmnv/spark,LantaoJin/spark,zzcclp/spark,apache-spark-on-k8s/spark,HyukjinKwon/spark,jlopezmalla/spark,liyichao/spark,loneknightpy/spark,sahilTakiar/spark,facaiy/spark,xuanyuanking/spark,someorz/spark,1haodian/spark,Panos-Bletsos/spark-cost-model-optimizer,MLnick/spark,markhamstra/spark,1haodian/spark,goldmedal/spark,bOOm-X/spark,akopich/spark,pgandhi999/spark,actuaryzhang/spark,highfei2011/spark,aosagie/spark,rednaxelafx/apache-spark,stanzhai/spark,ioana-delaney/spark,rednaxelafx/apache-spark,shaneknapp/spark,mdespriee/spark,huang1900/spark,ajaysaini725/spark,hhbyyh/spark,jkbradley/spark,publicRoman/spark,aray/spark,SHASHANKB/spark,mahak/spark,BryanCutler/spark,taroplus/spark,HyukjinKwon/spark,mike0sv/spark,brad-kaiser/spark,zhouyejoe/spark,adrian-ionescu/apache-spark,WeichenXu123/spark,map222/spark,JoshRosen/spark,Aegeaner/spark,kissmetrics/spark,zuotingbing/spark,rikima/spark,nlalevee/spark,kevinyu98/spark,kissmetrics/spark,mahak/spark,gengliangwang/spark,highfei2011/spark,ajaysaini725/spark,bravo-zhang/spark,rezasafi/spark,byakuinss/spark,yanboliang/spark,skonto/spark,yanboliang/spark,UndeadBaneGitHub/spark,huang1900/spark,mzl9039/spark,kevinyu98/spark,tengpeng/spark,tejasapatil/spark,metamx/spark,darionyaphet/spark,icexelloss/spark,jianran/spark,byakuinss/spark,yanboliang/spark,mzl9039/spark,aokolnychyi/spark,nlalevee/spark,Aegeaner/spark,big-pegasus/spark,saturday-shi/spark,huang1900/spark,HyukjinKwon/spark,gioenn/xSpark,publicRoman/spark,jianran/spark,yanboliang/spark,liutang123/spark,HyukjinKwon/spark,xuanyuanking/spark,markhamstra/spark,nlalevee/spark,alunarbeach/spark,bravo-zhang/spark,hvanhovell/spark,cin/spark,nilsgrabbert/spark,map222/spark,rikima/spark,holdenk/spark,akopich/spark,kissmetrics/spark,ueshin/apache-spark,gioenn/xSpark,lvdongr/spark,saltstar/spark,tejasapatil/spark,huang1900/spark,setjet/spark,sachintyagi22/spark,wangmiao1981/spark,patrick-nicholson/spark,milliman/spark,ron8hu/spark,SnappyDataInc/spark,stanzhai/spark,wzhfy/spark,maropu/spark,rezasafi/spark,sahilTakiar/spark,rekhajoshm/spark,shaneknapp/spark,gengliangwang/spark,yanboliang/spark,narahari92/spark,mdespriee/spark,icexelloss/spark,zuotingbing/spark,maropu/spark,witgo/spark,holdenk/spark,sachintyagi22/spark,lxsmnv/spark,debugger87/spark,milliman/spark,maropu/spark,byakuinss/spark,aokolnychyi/spark,aokolnychyi/spark,dhruve/spark,aosagie/spark,wangmiao1981/spark,markhamstra/spark,actuaryzhang/spark,pgandhi999/spark,esi-mineset/spark,markhamstra/spark,spark-test/spark,dbtsai/spark,caneGuy/spark,metamx/spark,tejasapatil/spark,xuanyuanking/spark,dhruve/spark,actuaryzhang/spark,poffuomo/spark,mike0sv/spark,ConeyLiu/spark,wangyum/spark,nchammas/spark,xuanyuanking/spark,publicRoman/spark,actuaryzhang/spark,actuaryzhang/spark,chuckchen/spark,xflin/spark,andrewor14/spark,rekhajoshm/spark,JoshRosen/spark,apache/spark,zero323/spark,esi-mineset/spark,ahnqirage/spark,bdrillard/spark,mdespriee/spark,UndeadBaneGitHub/spark,JerryLead/spark,maropu/spark,rikima/spark,narahari92/spark,holdenk/spark,sahilTakiar/spark,techaddict/spark,actuaryzhang/spark,shuangshuangwang/spark,kissmetrics/spark,highfei2011/spark,map222/spark,facaiy/spark,ptkool/spark,andrewor14/spark,dhruve/spark,WindCanDie/spark,skonto/spark,nchammas/spark,JerryLead/spark,hvanhovell/spark,minixalpha/spark,mdespriee/spark,kevinyu98/spark,ConeyLiu/spark,wangyum/spark,wangmiao1981/spark,shaneknapp/spark,bdrillard/spark,ron8hu/spark,big-pegasus/spark,big-pegasus/spark,janewangfb/spark,ConeyLiu/spark,alunarbeach/spark,spark-test/spark,setjet/spark,srowen/spark,cloud-fan/spark,shaneknapp/spark,HyukjinKwon/spark,pronix/spark,bOOm-X/spark,liutang123/spark,apache/spark,ueshin/apache-spark,nchammas/spark,vinodkc/spark,spark-test/spark,ahnqirage/spark,milliman/spark,xflin/spark,shuangshuangwang/spark,liyichao/spark,kiszk/spark,sachintyagi22/spark,sureshthalamati/spark,spark-test/spark,cin/spark,zhouyejoe/spark,zero323/spark,nilsgrabbert/spark,xflin/spark,ddna1021/spark,bravo-zhang/spark,patrick-nicholson/spark,publicRoman/spark,liutang123/spark,minixalpha/spark,taroplus/spark,guoxiaolongzte/spark,kimoonkim/spark,cloud-fan/spark,saturday-shi/spark,dongjoon-hyun/spark,ueshin/apache-spark,kiszk/spark,ericvandenbergfb/spark,sahilTakiar/spark,caneGuy/spark,ajaysaini725/spark,sureshthalamati/spark,taroplus/spark,akopich/spark,vinodkc/spark,kimoonkim/spark,loneknightpy/spark,haowu80s/spark,highfei2011/spark,Aegeaner/spark,witgo/spark,holdenk/spark,Panos-Bletsos/spark-cost-model-optimizer,ioana-delaney/spark,saturday-shi/spark,rikima/spark,apache-spark-on-k8s/spark,kimoonkim/spark,nchammas/spark,shaneknapp/spark,nlalevee/spark,map222/spark,mahak/spark,kevinyu98/spark,adrian-ionescu/apache-spark,dbtsai/spark,ajaysaini725/spark,zhouyejoe/spark,ron8hu/spark,rekhajoshm/spark,SnappyDataInc/spark,joseph-torres/spark,ahnqirage/spark,akopich/spark,hhbyyh/spark,dbtsai/spark,HyukjinKwon/spark,mdespriee/spark,kevinyu98/spark,dhruve/spark,rekhajoshm/spark,mzl9039/spark,zzcclp/spark,dhruve/spark,metamx/spark,ddna1021/spark,icexelloss/spark,janewangfb/spark,hvanhovell/spark,taroplus/spark,ibm-research-ireland/sparkoscope,liutang123/spark,joseph-torres/spark,pgandhi999/spark,HyukjinKwon/spark,eyalfa/spark,rezasafi/spark,gengliangwang/spark,akopich/spark,sureshthalamati/spark,ericvandenbergfb/spark,UndeadBaneGitHub/spark,loneknightpy/spark,aray/spark,szhem/spark,ahnqirage/spark,jlopezmalla/spark,michalsenkyr/spark,zhouyejoe/spark,bravo-zhang/spark,ron8hu/spark,narahari92/spark,guoxiaolongzte/spark,shubhamchopra/spark,alunarbeach/spark,nchammas/spark,UndeadBaneGitHub/spark,chuckchen/spark,dongjoon-hyun/spark,zhouyejoe/spark,kiszk/spark,aray/spark,matthewfranglen/spark,Panos-Bletsos/spark-cost-model-optimizer,shaneknapp/spark,wzhfy/spark,andrewor14/spark,tejasapatil/spark,ptkool/spark,jkbradley/spark,LantaoJin/spark,Panos-Bletsos/spark-cost-model-optimizer,MLnick/spark,goldmedal/spark,someorz/spark,shuangshuangwang/spark,rezasafi/spark,huang1900/spark,ueshin/apache-spark,tengpeng/spark,chuckchen/spark,eyalfa/spark,ibm-research-ireland/sparkoscope,chuckchen/spark,MLnick/spark,xflin/spark,jiangxb1987/spark,loneknightpy/spark,apache/spark,aokolnychyi/spark,zhouyejoe/spark,dbtsai/spark,joseph-torres/spark,patrick-nicholson/spark,narahari92/spark,goldmedal/spark,JerryLead/spark,jrshust/spark,zuotingbing/spark,facaiy/spark,rednaxelafx/apache-spark,zuotingbing/spark,dongjoon-hyun/spark,bOOm-X/spark,shubhamchopra/spark,milliman/spark,kissmetrics/spark,nchammas/spark,alunarbeach/spark,SHASHANKB/spark,mdespriee/spark,liyichao/spark,kevinyu98/spark,gioenn/xSpark,wzhfy/spark,hvanhovell/spark,BryanCutler/spark,akopich/spark,dhruve/spark,apache/spark,setjet/spark,ioana-delaney/spark,mike0sv/spark,aray/spark,zzcclp/spark,MLnick/spark,tejasapatil/spark,xuanyuanking/spark,zzcclp/spark,brad-kaiser/spark,markhamstra/spark,jrshust/spark,icexelloss/spark,stanzhai/spark,lvdongr/spark,map222/spark,lxsmnv/spark,caneGuy/spark,WindCanDie/spark,haowu80s/spark,tengpeng/spark,nilsgrabbert/spark,xuanyuanking/spark,janewangfb/spark,mdespriee/spark,shubhamchopra/spark,SHASHANKB/spark,mahak/spark,facaiy/spark,srowen/spark,WeichenXu123/spark,goldmedal/spark,panfengfeng/spark,JoshRosen/spark,techaddict/spark,adrian-ionescu/apache-spark,haowu80s/spark,lvdongr/spark,apache-spark-on-k8s/spark,janewangfb/spark,narahari92/spark,metamx/spark,ibm-research-ireland/sparkoscope,aosagie/spark,saltstar/spark,vinodkc/spark,WindCanDie/spark,eyalfa/spark,narahari92/spark,nilsgrabbert/spark,zuotingbing/spark,ibm-research-ireland/sparkoscope,kevinyu98/spark,milliman/spark,lxsmnv/spark,BryanCutler/spark,saturday-shi/spark,poffuomo/spark,brad-kaiser/spark,hhbyyh/spark,ahnqirage/spark,liutang123/spark,andrewor14/spark,alunarbeach/spark,nilsgrabbert/spark,wangmiao1981/spark,pgandhi999/spark,SnappyDataInc/spark,ddna1021/spark,bravo-zhang/spark,szhem/spark,stanzhai/spark,xflin/spark,apache/spark,ptkool/spark,narahari92/spark,aokolnychyi/spark,publicRoman/spark,lxsmnv/spark,ConeyLiu/spark,nlalevee/spark,caneGuy/spark,jrshust/spark,byakuinss/spark,janewangfb/spark,minixalpha/spark,caneGuy/spark,SnappyDataInc/spark,haowu80s/spark,skonto/spark,srowen/spark,WeichenXu123/spark,cin/spark,ptkool/spark,cin/spark,UndeadBaneGitHub/spark,nchammas/spark,ConeyLiu/spark,Aegeaner/spark,esi-mineset/spark,sahilTakiar/spark,joseph-torres/spark,srowen/spark,holdenk/spark,highfei2011/spark,nlalevee/spark,michalsenkyr/spark,bdrillard/spark,witgo/spark,wangyum/spark,someorz/spark,panfengfeng/spark,sachintyagi22/spark,MLnick/spark,wangmiao1981/spark