fix io bugs in bucket spliting
fix io bugs in bucket spliting

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