Merge pull request #11560 from ukernel/wip-mds-context-wrapping

MDS: reduce usage of context wrapper

Reviewed-by: John Spray <john.spray@redhat.com>

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

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

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

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

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