ddl: add find index test for index schema change.
ddl: add find index test for index schema change.

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