[example] fix ddpg bug (#4078)
[example] fix ddpg bug (#4078)


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