ddl_test: use mock tikv store (#4655)
ddl_test: use mock tikv store (#4655)


zimulala/tidb,ngaut/tidb,pingcap/tidb,pingcap/tidb,cosmtrek/tidb,pingcap/tidb,XuHuaiyu/tidb,ngaut/tidb,mccxj/tidb,XuHuaiyu/tidb,c4pt0r/tidb,c4pt0r/tidb,louishust/tidb,kyle-wang/tidb,yuanwhy/tidb,kyle-wang/tidb,CodeRushing/tidb,c4pt0r/tidb,zimulala/tidb,kyle-wang/tidb,tiancaiamao/tidb,ngaut/tidb,ngaut/tidb,ngaut/tidb,CodeRushing/tidb,8cbx/tidb,yangwenmai/tidb,pingcap/tidb,c4pt0r/tidb,cosmtrek/tidb,Cofyc/tidb,c4pt0r/tidb,Nify/tidb,wusphinx/tidb,mccxj/tidb,spongedu/tidb,EvilMcJerkface/tidb,tiancaiamao/tidb,wusphinx/tidb,kyle-wang/tidb,ngaut/tidb,coocood/tidb,c4pt0r/tidb,Cofyc/tidb,ming-relax/tidb,pingcap/tidb,kyle-wang/tidb,yuanwhy/tidb,qiuyesuifeng/tidb,Nify/tidb,coocood/tidb,qiuyesuifeng/tidb,EvilMcJerkface/tidb,ming-relax/tidb,louishust/tidb,yangwenmai/tidb,pingcap/tidb,8cbx/tidb,spongedu/tidb,kyle-wang/tidb