localstore: add multi key inc test.
localstore: add multi key inc test.

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