Fix balance-leader won't work when placement rule enabled (#2725)#2726

Merged

disksing merged 1 commit intotikv:release-4.0from ti-srebot:release-4.0-33666d8aaa97

Aug 6, 2020

+106-35

Commits on Aug 6, 2020

cherry pick tikv#2725 to release-4.0

Yisaer
authored and
ti-srebot
committed