update launch.py if yarn.submit without hostfile (#2991)
update launch.py if yarn.submit without hostfile (#2991)

hostfile is required for ssh and mpi, if hostfile is missed, "{local, yarn, sge}" should be available
antoan2/incubator-mxnet,Northrend/mxnet,ZihengJiang/mxnet,smolix/incubator-mxnet,jiajiechen/mxnet,sergeykolychev/mxnet,piiswrong/mxnet,weleen/mxnet,stefanhenneking/mxnet,solin319/incubator-mxnet,apaleyes/mxnet,Northrend/mxnet,arank/mxnet,jermainewang/mxnet,solin319/incubator-mxnet,LinkHS/incubator-mxnet,jermainewang/mxnet,navrasio/mxnet,likelyzhao/mxnet,tlby/mxnet,hesseltuinhof/mxnet,ShownX/incubator-mxnet,LinkHS/incubator-mxnet,CodingCat/mxnet,mbaijal/incubator-mxnet,arank/mxnet,jennyzhang0215/incubator-mxnet,eric-haibin-lin/mxnet,hesseltuinhof/mxnet,Ldpe2G/mxnet,rishita/mxnet,precedenceguo/mxnet,nicklhy/mxnet,thirdwing/mxnet,precedenceguo/mxnet,apaleyes/mxnet,TuSimple/mxnet,hesseltuinhof/mxnet,ForkedReposBak/mxnet,kkk669/mxnet,nicklhy/mxnet,ykim362/mxnet,yajiedesign/mxnet,gautamkmr/incubator-mxnet,ShownX/incubator-mxnet,crazy-cat/incubator-mxnet,thirdwing/mxnet,likelyzhao/mxnet,gautamkmr/incubator-mxnet,weleen/mxnet,EvanzzzZ/mxnet,pluskid/mxnet,lxn2/mxnet,Mega-DatA-Lab/mxnet,zhreshold/mxnet,smolix/incubator-mxnet,LinkHS/incubator-mxnet,likelyzhao/mxnet,vikingMei/mxnet,TuSimple/mxnet,hotpxl/mxnet,formath/mxnet,xcgoner/dist-mxnet,tlby/mxnet,larroy/mxnet,zhreshold/mxnet,kkk669/mxnet,reminisce/mxnet,lxn2/mxnet,larroy/mxnet,danithaca/mxnet,nicklhy/mxnet,apache/incubator-mxnet,navrasio/mxnet,lxn2/mxnet,navrasio/mxnet,DR08/mxnet,kkk669/mxnet,hesseltuinhof/mxnet,madjam/mxnet,fullfanta/mxnet,pluskid/mxnet,dmlc/mxnet,jermainewang/mxnet,eric-haibin-lin/mxnet,hotpxl/mxnet,madjam/mxnet,gautamkmr/incubator-mxnet,szha/mxnet,antoan2/incubator-mxnet,dmlc/mxnet,ykim362/mxnet,apaleyes/mxnet,Mega-DatA-Lab/mxnet,TuSimple/mxnet,rishita/mxnet,vikingMei/mxnet,smolix/incubator-mxnet,indhub/mxnet,Mega-DatA-Lab/mxnet,tlby/mxnet,ptrendx/mxnet,Northrend/mxnet,apaleyes/mxnet,luoyetx/mxnet,szha/mxnet,kevinthesun/mxnet,apache/incubator-mxnet,szha/mxnet,EvanzzzZ/mxnet,coder-james/mxnet,nicklhy/mxnet,dmlc/mxnet,Mega-DatA-Lab/mxnet,sergeykolychev/mxnet,indhub/mxnet,apaleyes/mxnet,wangyum/mxnet,eric-haibin-lin/mxnet,hotpxl/mxnet,tlby/mxnet,kkk669/mxnet,CodingCat/mxnet,kevinthesun/mxnet,fullfanta/mxnet,yuruofeifei/mxnet,Prasad9/incubator-mxnet,saurabh3949/mxnet,sxjscience/mxnet,lxn2/mxnet,leezu/mxnet,zhreshold/mxnet,Ldpe2G/mxnet,jermainewang/mxnet,antoan2/incubator-mxnet,navrasio/mxnet,sxjscience/mxnet,hesseltuinhof/mxnet,jennyzhang0215/incubator-mxnet,TuSimple/mxnet,ZihengJiang/mxnet,precedenceguo/mxnet,zhreshold/mxnet,mbaijal/incubator-mxnet,reminisce/mxnet,EvanzzzZ/mxnet,jennyzhang0215/incubator-mxnet,CodingCat/mxnet,mbaijal/incubator-mxnet,tornadomeet/mxnet,luoyetx/mxnet,smolix/incubator-mxnet,sxjscience/mxnet,sergeykolychev/mxnet,Mega-DatA-Lab/mxnet,coder-james/mxnet,hesseltuinhof/mxnet,EvanzzzZ/mxnet,eric-haibin-lin/mxnet,danithaca/mxnet,ZihengJiang/mxnet,jamesliu/mxnet,Guneet-Dhillon/mxnet,ForkedReposBak/mxnet,zhreshold/mxnet,leezu/mxnet,kevinthesun/mxnet,sergeykolychev/mxnet,yajiedesign/mxnet,crazy-cat/incubator-mxnet,TuSimple/mxnet,rishita/mxnet,Guneet-Dhillon/mxnet,dmlc/mxnet,reminisce/mxnet,crazy-cat/incubator-mxnet,navrasio/mxnet,antoan2/incubator-mxnet,EvanzzzZ/mxnet,Northrend/mxnet,jennyzhang0215/incubator-mxnet,DR08/mxnet,arank/mxnet,TuSimple/mxnet,thirdwing/mxnet,saurabh3949/mxnet,DR08/mxnet,ykim362/mxnet,tornadomeet/mxnet,yuruofeifei/mxnet,crazy-cat/incubator-mxnet,Guneet-Dhillon/mxnet,jennyzhang0215/incubator-mxnet,saurabh3949/mxnet,gautamkmr/incubator-mxnet,apaleyes/mxnet,rishita/mxnet,solin319/incubator-mxnet,Prasad9/incubator-mxnet,precedenceguo/mxnet,antoan2/incubator-mxnet,hpi-xnor/BMXNet,arikpoz/mxnet,jamesliu/mxnet,ykim362/mxnet,luoyetx/mxnet,solin319/incubator-mxnet,ZihengJiang/mxnet,tornadomeet/mxnet,precedenceguo/mxnet,dmlc/mxnet,piiswrong/mxnet,wangyum/mxnet,eric-haibin-lin/mxnet,ZihengJiang/mxnet,jiajiechen/mxnet,Ldpe2G/mxnet,sxjscience/mxnet,wangyum/mxnet,DickJC123/mxnet,ForkedReposBak/mxnet,larroy/mxnet,ForkedReposBak/mxnet,mbaijal/incubator-mxnet,vikingMei/mxnet,fullfanta/mxnet,leezu/mxnet,rahul003/mxnet,Guneet-Dhillon/mxnet,tornadomeet/mxnet,luoyetx/mxnet,hesseltuinhof/mxnet,thirdwing/mxnet,nicklhy/mxnet,larroy/mxnet,yajiedesign/mxnet,TuSimple/mxnet,tlby/mxnet,stefanhenneking/mxnet,Ldpe2G/mxnet,yuruofeifei/mxnet,antoan2/incubator-mxnet,vikingMei/mxnet,wangyum/mxnet,thirdwing/mxnet,weleen/mxnet,likelyzhao/mxnet,EvanzzzZ/mxnet,formath/mxnet,jennyzhang0215/incubator-mxnet,jamesliu/mxnet,eric-haibin-lin/mxnet,crazy-cat/incubator-mxnet,hpi-xnor/BMXNet,hesseltuinhof/mxnet,Prasad9/incubator-mxnet,yuruofeifei/mxnet,kevinthesun/mxnet,vikingMei/mxnet,piiswrong/mxnet,ShownX/incubator-mxnet,smolix/incubator-mxnet,likelyzhao/mxnet,jermainewang/mxnet,leezu/mxnet,gautamkmr/incubator-mxnet,kevinthesun/mxnet,likelyzhao/mxnet,fullfanta/mxnet,hotpxl/mxnet,rahul003/mxnet,Northrend/mxnet,ykim362/mxnet,fullfanta/mxnet,crazy-cat/incubator-mxnet,Ldpe2G/mxnet,EvanzzzZ/mxnet,gautamkmr/incubator-mxnet,Ldpe2G/mxnet,rahul003/mxnet,xcgoner/dist-mxnet,wangyum/mxnet,likelyzhao/mxnet,arikpoz/mxnet,jermainewang/mxnet,madjam/mxnet,piiswrong/mxnet,sxjscience/mxnet,Guneet-Dhillon/mxnet,arank/mxnet,indhub/mxnet,hpi-xnor/BMXNet,apaleyes/mxnet,CodingCat/mxnet,Northrend/mxnet,pluskid/mxnet,DR08/mxnet,dmlc/mxnet,smolix/incubator-mxnet,Mega-DatA-Lab/mxnet,leezu/mxnet,indhub/mxnet,arikpoz/mxnet,sxjscience/mxnet,larroy/mxnet,Mega-DatA-Lab/mxnet,ForkedReposBak/mxnet,jamesliu/mxnet,LinkHS/incubator-mxnet,precedenceguo/mxnet,jiajiechen/mxnet,sergeykolychev/mxnet,xcgoner/dist-mxnet,tlby/mxnet,jiajiechen/mxnet,solin319/incubator-mxnet,madjam/mxnet,navrasio/mxnet,reminisce/mxnet,hotpxl/mxnet,piiswrong/mxnet,sxjscience/mxnet,arank/mxnet,coder-james/mxnet,jennyzhang0215/incubator-mxnet,leezu/mxnet,smolix/incubator-mxnet,arikpoz/mxnet,zhreshold/mxnet,crazy-cat/incubator-mxnet,kkk669/mxnet,DR08/mxnet,indhub/mxnet,danithaca/mxnet,vikingMei/mxnet,solin319/incubator-mxnet,kkk669/mxnet,sergeykolychev/mxnet,pluskid/mxnet,stefanhenneking/mxnet,hotpxl/mxnet,mbaijal/incubator-mxnet,ShownX/incubator-mxnet,CodingCat/mxnet,LinkHS/incubator-mxnet,precedenceguo/mxnet,crazy-cat/incubator-mxnet,CodingCat/mxnet,yuruofeifei/mxnet,rahul003/mxnet,wangyum/mxnet,kkk669/mxnet,reminisce/mxnet,rishita/mxnet,Mega-DatA-Lab/mxnet,saurabh3949/mxnet,larroy/mxnet,ptrendx/mxnet,thirdwing/mxnet,yajiedesign/mxnet,Guneet-Dhillon/mxnet,lxn2/mxnet,madjam/mxnet,apache/incubator-mxnet,jamesliu/mxnet,szha/mxnet,coder-james/mxnet,pluskid/mxnet,rishita/mxnet,piiswrong/mxnet,CodingCat/mxnet,thirdwing/mxnet,kevinthesun/mxnet,xcgoner/dist-mxnet,eric-haibin-lin/mxnet,kkk669/mxnet,reminisce/mxnet,rahul003/mxnet,DickJC123/mxnet,DR08/mxnet,Prasad9/incubator-mxnet,ptrendx/mxnet,yuruofeifei/mxnet,zhreshold/mxnet,fullfanta/mxnet,fullfanta/mxnet,Northrend/mxnet,lxn2/mxnet,tornadomeet/mxnet,tlby/mxnet,pluskid/mxnet,pluskid/mxnet,ptrendx/mxnet,leezu/mxnet,yuruofeifei/mxnet,coder-james/mxnet,tlby/mxnet,madjam/mxnet,kevinthesun/mxnet,mbaijal/incubator-mxnet,smolix/incubator-mxnet,reminisce/mxnet,danithaca/mxnet,hotpxl/mxnet,eric-haibin-lin/mxnet,ptrendx/mxnet,madjam/mxnet,xcgoner/dist-mxnet,jennyzhang0215/incubator-mxnet,Prasad9/incubator-mxnet,Northrend/mxnet,ptrendx/mxnet,solin319/incubator-mxnet,yajiedesign/mxnet,jermainewang/mxnet,formath/mxnet,gautamkmr/incubator-mxnet,precedenceguo/mxnet,ShownX/incubator-mxnet,wangyum/mxnet,szha/mxnet,TuSimple/mxnet,zhreshold/mxnet,jamesliu/mxnet,mbaijal/incubator-mxnet,apaleyes/mxnet,gautamkmr/incubator-mxnet,weleen/mxnet,luoyetx/mxnet,piiswrong/mxnet,ZihengJiang/mxnet,LinkHS/incubator-mxnet,formath/mxnet,piiswrong/mxnet,lxn2/mxnet,tornadomeet/mxnet,xcgoner/dist-mxnet,EvanzzzZ/mxnet,vikingMei/mxnet,tornadomeet/mxnet,LinkHS/incubator-mxnet,EvanzzzZ/mxnet,jiajiechen/mxnet,piiswrong/mxnet,luoyetx/mxnet,DR08/mxnet,eric-haibin-lin/mxnet,arikpoz/mxnet,arank/mxnet,stefanhenneking/mxnet,DickJC123/mxnet,ZihengJiang/mxnet,pluskid/mxnet,luoyetx/mxnet,tlby/mxnet,pluskid/mxnet,xcgoner/dist-mxnet,jamesliu/mxnet,ptrendx/mxnet,tlby/mxnet,rahul003/mxnet,hotpxl/mxnet,sergeykolychev/mxnet,yuruofeifei/mxnet,saurabh3949/mxnet,hpi-xnor/BMXNet,Ldpe2G/mxnet,reminisce/mxnet,hpi-xnor/BMXNet,arikpoz/mxnet,madjam/mxnet,danithaca/mxnet,kevinthesun/mxnet,rishita/mxnet,leezu/mxnet,saurabh3949/mxnet,lxn2/mxnet,hpi-xnor/BMXNet,rahul003/mxnet,stefanhenneking/mxnet,arikpoz/mxnet,wangyum/mxnet,LinkHS/incubator-mxnet,arank/mxnet,formath/mxnet,ptrendx/mxnet,ptrendx/mxnet,lxn2/mxnet,danithaca/mxnet,indhub/mxnet,nicklhy/mxnet,stefanhenneking/mxnet,hesseltuinhof/mxnet,leezu/mxnet,ykim362/mxnet,indhub/mxnet,indhub/mxnet,stefanhenneking/mxnet,danithaca/mxnet,ShownX/incubator-mxnet,vikingMei/mxnet,jiajiechen/mxnet,nicklhy/mxnet,stefanhenneking/mxnet,hpi-xnor/BMXNet,jiajiechen/mxnet,fullfanta/mxnet,Guneet-Dhillon/mxnet,jermainewang/mxnet,arikpoz/mxnet,formath/mxnet,jamesliu/mxnet,sxjscience/mxnet,reminisce/mxnet,ShownX/incubator-mxnet,navrasio/mxnet,coder-james/mxnet,danithaca/mxnet,jermainewang/mxnet,coder-james/mxnet,antoan2/incubator-mxnet,hpi-xnor/BMXNet,ShownX/incubator-mxnet,solin319/incubator-mxnet,indhub/mxnet,madjam/mxnet,dmlc/mxnet,szha/mxnet,tornadomeet/mxnet,wangyum/mxnet,weleen/mxnet,rishita/mxnet,ZihengJiang/mxnet,rahul003/mxnet,rahul003/mxnet,TuSimple/mxnet,mbaijal/incubator-mxnet,saurabh3949/mxnet,TuSimple/mxnet,jamesliu/mxnet,ForkedReposBak/mxnet,szha/mxnet,precedenceguo/mxnet,fullfanta/mxnet,Prasad9/incubator-mxnet,jiajiechen/mxnet,Mega-DatA-Lab/mxnet,rishita/mxnet,DR08/mxnet,ykim362/mxnet,weleen/mxnet,weleen/mxnet,yajiedesign/mxnet,danithaca/mxnet,arikpoz/mxnet,CodingCat/mxnet,luoyetx/mxnet,reminisce/mxnet,Prasad9/incubator-mxnet,larroy/mxnet,ForkedReposBak/mxnet,Prasad9/incubator-mxnet,LinkHS/incubator-mxnet,ykim362/mxnet,navrasio/mxnet,jiajiechen/mxnet,dmlc/mxnet,formath/mxnet,arank/mxnet,tornadomeet/mxnet,stefanhenneking/mxnet,nicklhy/mxnet,yajiedesign/mxnet,DR08/mxnet,weleen/mxnet,gautamkmr/incubator-mxnet,mbaijal/incubator-mxnet,jennyzhang0215/incubator-mxnet,solin319/incubator-mxnet,szha/mxnet,Prasad9/incubator-mxnet,antoan2/incubator-mxnet,formath/mxnet,hotpxl/mxnet,crazy-cat/incubator-mxnet,likelyzhao/mxnet,ForkedReposBak/mxnet,kevinthesun/mxnet,ForkedReposBak/mxnet,yajiedesign/mxnet,sergeykolychev/mxnet,hpi-xnor/BMXNet,ShownX/incubator-mxnet,vikingMei/mxnet,saurabh3949/mxnet,xcgoner/dist-mxnet,sxjscience/mxnet,Guneet-Dhillon/mxnet,sergeykolychev/mxnet,ykim362/mxnet,likelyzhao/mxnet,zhreshold/mxnet,Ldpe2G/mxnet,coder-james/mxnet,weleen/mxnet,apaleyes/mxnet,DickJC123/mxnet,larroy/mxnet,smolix/incubator-mxnet,szha/mxnet,ptrendx/mxnet,antoan2/incubator-mxnet,larroy/mxnet,Northrend/mxnet,yajiedesign/mxnet,yuruofeifei/mxnet,apache/incubator-mxnet,CodingCat/mxnet,arank/mxnet,saurabh3949/mxnet,luoyetx/mxnet,Ldpe2G/mxnet,ZihengJiang/mxnet,Guneet-Dhillon/mxnet,thirdwing/mxnet,dmlc/mxnet,formath/mxnet,nicklhy/mxnet,thirdwing/mxnet,kkk669/mxnet,navrasio/mxnet,coder-james/mxnet,xcgoner/dist-mxnet