Merge pull request #7798 from ukernel/wip-mds-snap

A few more snapshot fixes, mostly around snapshotted inode/dentry tracking

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

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

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

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

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