Merge PR 16068 into master

Merge PR 16068 into master

* refs/remotes/upstream/pull/16068/head:
	mds: wait auth pinned objects when deactivating mds
	mds: fix "wait for stray manager to start"
	ceph: kick purge queue when mds active
	mds: properly do null snapflush
	mds: force client to flush data when waiting on LOCK_SNAP_SYNC lock
	mds: don't issue caps for frozen inode

Reviewed-by: Patrick Donnelly <pdonnell@redhat.com>