Merge pull request #12537 from liewegas/wip-optracker

common/TrackedOp: various cleanups and optimizations

Reviewed-by: Greg Farnum <gfarnum@redhat.com>

diff --cc src/CMakeLists.txt
Simple merge

diff --cc src/mds/MDCache.cc
Simple merge

diff --cc src/mds/MDCache.h
Simple merge

diff --cc src/mds/Server.cc
Simple merge