tables tests: replace cnt + 1 to cnt++ golint warning
tables tests: replace cnt + 1 to cnt++
golint warning

kyle-wang/tidb,yuanwhy/tidb,Cofyc/tidb,silenceper/tidb,ming-relax/tidb,c4pt0r/tidb,silenceper/tidb,coocood/tidb,8cbx/tidb,anywhy/tidb,simon-xia/tidb,louishust/tidb,XuHuaiyu/tidb,zs634134578/tidb,ngaut/tidb,silentred/tidb,louishust/tidb,wusphinx/tidb,tiancaiamao/tidb,gaocegege/tidb,pingcap/tidb,simon-xia/tidb,XuHuaiyu/tidb,c4pt0r/tidb,ueizhou/tidb,mccxj/tidb,Cofyc/tidb,coocood/tidb,astaxie/tidb,myrice/tidb,yuanwhy/tidb,silentred/tidb,8cbx/tidb,Nify/tidb,qiuyesuifeng/tidb,c4pt0r/tidb,cosmtrek/tidb,zimulala/tidb,zimulala/tidb,kyle-wang/tidb,c4pt0r/tidb,CodeRushing/tidb,qhsong/tidb,kyle-wang/tidb,kyle-wang/tidb,myrice/tidb,netroby/tidb,qiuyesuifeng/tidb,ngaut/tidb,CodeRushing/tidb,yangwenmai/tidb,andelf/tidb,pingcap/tidb,cosmtrek/tidb,ngaut/tidb,andelf/tidb,c4pt0r/tidb,ngaut/tidb,ngaut/tidb,anywhy/tidb,EvilMcJerkface/tidb,zs634134578/tidb,kyle-wang/tidb,JinheLin/tidb,spongedu/tidb,EvilMcJerkface/tidb,Nify/tidb,JinheLin/tidb,kyle-wang/tidb,spongedu/tidb,c4pt0r/tidb,pingcap/tidb,ming-relax/tidb,mccxj/tidb,netroby/tidb,astaxie/tidb,liyu4/tidb,tiancaiamao/tidb,wusphinx/tidb,ueizhou/tidb,pingcap/tidb,yangwenmai/tidb,qhsong/tidb,gaocegege/tidb,ngaut/tidb,pingcap/tidb,liyu4/tidb,pingcap/tidb