Merge PR #35944 into master

* refs/pull/35944/head:
	qa: defer cleaning the mountpoint's netnses and the bridge
	qa/tasks/cephfs/mount.py: remove the stale netnses and bridge
	qa/tasks/cephfs/mount.py: try to flush the stale ceph-brx dev info
	qa/tasks/cephfs/mount.py: switch to run_shell_payload() helper
	qa/tasks/cephfs/mount.py: clean up the none used code

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