scheduler: revert low space threshold hard limit (#2864)#2875

Merged

disksing merged 1 commit intotikv:release-4.0from ti-srebot:release-4.0-df2344f251ce

Sep 1, 2020

+10-41

Commits on Sep 1, 2020

cherry pick tikv#2864 to release-4.0

rleungx
authored and
ti-srebot
committed