Merge PR #22668 into master

Merge PR #22668 into master

* refs/pull/22668/head:
	mds: reorganize and curate perf log counters
	mds: show session load average in dump session
	mds: allow request load average decay rate configurable via admin socket
	mds: decay counter for tracking request load average
	mds: add perf counters to track current open/stale sessions

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