Merge PR #24270 into master

Merge PR #24270 into master

* refs/pull/24270/head:
	osd: make 'cache drop' command require 'executable' permission
	osd: rename 'drop cache' and 'get cache stats' to group them by component
	doc: add documentation for 'drop cache' and 'get cache stats'
	osd: don't print osdmap cache stats in 'get cache stats' command
	osd: do not clear osdmap cache on 'drop cache' command
	osd: offload dumping cache stats to the object store
	osd: pass a stream to flush_cache commands for more verbosity
	osd: implement flush_cache() method for Filestore
	osd: add clear_cache and get_cache_object_count commands

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