[SPARK-25287][INFRA] Add up-front check for JIRA_USERNAME and JIRA_PASSWORD
[SPARK-25287][INFRA] Add up-front check for JIRA_USERNAME and JIRA_PASSWORD

## What changes were proposed in this pull request?

Add an up-front check that `JIRA_USERNAME` and `JIRA_PASSWORD` have been set. If they haven't, ask user if they want to continue. This prevents the JIRA state update from failing at the very end of the process because user forgot to set these environment variables.

## How was this patch tested?

I ran the script with environment vars set, and unset, to verify it works as specified.

Please review http://spark.apache.org/contributing.html before opening a pull request.

Closes #22294 from erikerlandson/spark-25287.

Authored-by: Erik Erlandson <4f562d7e9a779961be2e13fa744c0b21e1eef00c@redhat.com>
Signed-off-by: Erik Erlandson <4f562d7e9a779961be2e13fa744c0b21e1eef00c@redhat.com>

shuangshuangwang/spark,bdrillard/spark,apache/spark,highfei2011/spark,yanboliang/spark,pgandhi999/spark,ahnqirage/spark,techaddict/spark,techaddict/spark,zuotingbing/spark,srowen/spark,guoxiaolongzte/spark,JoshRosen/spark,aosagie/spark,hhbyyh/spark,apache/spark,goldmedal/spark,highfei2011/spark,zzcclp/spark,yanboliang/spark,xuanyuanking/spark,ahnqirage/spark,JoshRosen/spark,shaneknapp/spark,zero323/spark,ueshin/apache-spark,michalsenkyr/spark,holdenk/spark,WeichenXu123/spark,wangmiao1981/spark,mdespriee/spark,goldmedal/spark,kevinyu98/spark,taroplus/spark,facaiy/spark,rednaxelafx/apache-spark,rezasafi/spark,highfei2011/spark,hvanhovell/spark,hhbyyh/spark,zzcclp/spark,hvanhovell/spark,LantaoJin/spark,techaddict/spark,WeichenXu123/spark,icexelloss/spark,witgo/spark,rednaxelafx/apache-spark,maropu/spark,BryanCutler/spark,srowen/spark,gengliangwang/spark,maropu/spark,witgo/spark,rekhajoshm/spark,ptkool/spark,gengliangwang/spark,rekhajoshm/spark,jiangxb1987/spark,skonto/spark,michalsenkyr/spark,kiszk/spark,icexelloss/spark,WindCanDie/spark,guoxiaolongzte/spark,wangyum/spark,ConeyLiu/spark,hhbyyh/spark,pgandhi999/spark,dongjoon-hyun/spark,rekhajoshm/spark,srowen/spark,srowen/spark,spark-test/spark,ConeyLiu/spark,dbtsai/spark,spark-test/spark,rednaxelafx/apache-spark,kiszk/spark,LantaoJin/spark,goldmedal/spark,wangyum/spark,zuotingbing/spark,kevinyu98/spark,witgo/spark,ahnqirage/spark,WindCanDie/spark,aosagie/spark,aosagie/spark,yanboliang/spark,caneGuy/spark,chuckchen/spark,zhouyejoe/spark,guoxiaolongzte/spark,techaddict/spark,zhouyejoe/spark,lvdongr/spark,witgo/spark,dbtsai/spark,techaddict/spark,apache/spark,zzcclp/spark,xuanyuanking/spark,jkbradley/spark,milliman/spark,dongjoon-hyun/spark,guoxiaolongzte/spark,srowen/spark,zuotingbing/spark,kiszk/spark,lvdongr/spark,xuanyuanking/spark,aosagie/spark,actuaryzhang/spark,techaddict/spark,shaneknapp/spark,Aegeaner/spark,darionyaphet/spark,spark-test/spark,chuckchen/spark,gengliangwang/spark,michalsenkyr/spark,wangmiao1981/spark,wangyum/spark,WeichenXu123/spark,icexelloss/spark,ueshin/apache-spark,bdrillard/spark,rezasafi/spark,BryanCutler/spark,icexelloss/spark,shuangshuangwang/spark,chuckchen/spark,LantaoJin/spark,HyukjinKwon/spark,milliman/spark,mdespriee/spark,ptkool/spark,ueshin/apache-spark,techaddict/spark,actuaryzhang/spark,bdrillard/spark,milliman/spark,zero323/spark,aosagie/spark,LantaoJin/spark,wangyum/spark,kevinyu98/spark,zhouyejoe/spark,WeichenXu123/spark,hvanhovell/spark,wangyum/spark,hhbyyh/spark,rednaxelafx/apache-spark,skonto/spark,spark-test/spark,wzhfy/spark,BryanCutler/spark,bdrillard/spark,skonto/spark,mahak/spark,JoshRosen/spark,hhbyyh/spark,actuaryzhang/spark,goldmedal/spark,shuangshuangwang/spark,caneGuy/spark,maropu/spark,zzcclp/spark,LantaoJin/spark,srowen/spark,HyukjinKwon/spark,cloud-fan/spark,ahnqirage/spark,JoshRosen/spark,HyukjinKwon/spark,lvdongr/spark,lvdongr/spark,WindCanDie/spark,witgo/spark,mdespriee/spark,icexelloss/spark,zzcclp/spark,witgo/spark,dbtsai/spark,zero323/spark,caneGuy/spark,pgandhi999/spark,JoshRosen/spark,bdrillard/spark,zhouyejoe/spark,WeichenXu123/spark,hvanhovell/spark,chuckchen/spark,rednaxelafx/apache-spark,LantaoJin/spark,wangmiao1981/spark,darionyaphet/spark,rezasafi/spark,ptkool/spark,yanboliang/spark,goldmedal/spark,ahnqirage/spark,hvanhovell/spark,michalsenkyr/spark,JoshRosen/spark,darionyaphet/spark,Aegeaner/spark,apache/spark,yanboliang/spark,ptkool/spark,Aegeaner/spark,Aegeaner/spark,shaneknapp/spark,zhouyejoe/spark,spark-test/spark,zero323/spark,yanboliang/spark,rezasafi/spark,srowen/spark,zzcclp/spark,taroplus/spark,dbtsai/spark,mahak/spark,nchammas/spark,WeichenXu123/spark,gengliangwang/spark,zero323/spark,goldmedal/spark,mahak/spark,milliman/spark,michalsenkyr/spark,rezasafi/spark,zero323/spark,kevinyu98/spark,nchammas/spark,dongjoon-hyun/spark,jkbradley/spark,cloud-fan/spark,Aegeaner/spark,zhouyejoe/spark,dbtsai/spark,lvdongr/spark,WindCanDie/spark,taroplus/spark,ConeyLiu/spark,cloud-fan/spark,hvanhovell/spark,dbtsai/spark,kiszk/spark,bdrillard/spark,jiangxb1987/spark,vinodkc/spark,darionyaphet/spark,ptkool/spark,actuaryzhang/spark,vinodkc/spark,ConeyLiu/spark,taroplus/spark,pgandhi999/spark,jkbradley/spark,shaneknapp/spark,dongjoon-hyun/spark,darionyaphet/spark,shuangshuangwang/spark,apache/spark,hvanhovell/spark,vinodkc/spark,ConeyLiu/spark,apache/spark,skonto/spark,ConeyLiu/spark,guoxiaolongzte/spark,nchammas/spark,wangmiao1981/spark,shaneknapp/spark,BryanCutler/spark,xuanyuanking/spark,nchammas/spark,ahnqirage/spark,zuotingbing/spark,nchammas/spark,pgandhi999/spark,holdenk/spark,darionyaphet/spark,lvdongr/spark,WindCanDie/spark,ueshin/apache-spark,ueshin/apache-spark,aosagie/spark,wzhfy/spark,guoxiaolongzte/spark,hhbyyh/spark,Aegeaner/spark,caneGuy/spark,michalsenkyr/spark,dbtsai/spark,wangmiao1981/spark,pgandhi999/spark,kiszk/spark,jiangxb1987/spark,JoshRosen/spark,chuckchen/spark,matthewfranglen/spark,icexelloss/spark,kiszk/spark,jiangxb1987/spark,holdenk/spark,zzcclp/spark,mdespriee/spark,Br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