Merge PR #16778 into master

* refs/remotes/upstream/pull/16778/head:
	mds: fix return value of MDCache::dump_cache
	mds: new cap message flags indicate if there is pending capsnap
	mds: properly do null snapflush part2
	mds: track snap inodes through sorted map
	mds: properly drop wrlock when finishing snapflush

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

diff --cc src/client/Client.cc
Simple merge