Merge PR #21885 into master

Merge PR #21885 into master

* refs/pull/21885/head:
	qa: update cluster log health warning message
	qa: add tests for client features
	mds: evict clients that lack required features
	mds: cleanup MDSRank::evict_client
	mds: infer client version by client metadata and connection's features
	mds: introduce "ceph fs set <fs_name> min_compat_client <release_name>"
	mds: tell client why it's rejected
	mds: introduce cephfs' own feature bits
	mds: make Server::prepare_force_open_sessions() update client metadata

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