Merge pull request #4737 from kylinstorage/wip-temp-based-object-eviction

osd: improve temperature calculation for cache tier agent

Reviewed-by: Sage Weil

diff --cc src/common/config_opts.h
Simple merge

diff --cc src/osd/ReplicatedPG.cc
Simple merge

diff --cc src/test/librados/tier.cc
Simple merge