Merge PR #29926 into nautilus

* refs/pull/29926/head:
	mgr/volumes: return string type to ceph-manager
	qa/tasks: test for prevent negative subvolume size
	mgr/volumes: prevent negative subvolume size
	mgr/volumes: drop unnecessary size
	mgr/volumes: cleanup FS subvolume or subvolume group path
	mgr/volumes: give useful error message

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