tidb-server: set store default value to goleveldb (#4285)
tidb-server: set store default value to goleveldb (#4285)


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