planner: fix panic of merge join for tables with redundant indexes (#15840)#15918

Merged

eurekaka merged 3 commits intopingcap:release-2.1from sre-bot:release-2.1-10de222741de

Apr 1, 2020

+13-1

Commits on Mar 27, 2020

resolve conflicts
eurekaka
committed

Commits on Mar 31, 2020

cherry pick pingcap#15840 to release-2.1

eurekaka
authored and
sre-bot
committed

Commits on Apr 1, 2020

Merge branch 'release-2.1' into release-2.1-10de222741de
eurekaka
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