Merge PR #43936 into master

* refs/pull/43936/head:
	qa/tasks/cephadm: pull image to all hosts in parallel
	qa/tasks/cephadm: add hosts via mon remote
	qa/tasks/cephadm: use shortname for remote directory
	qa/tasks/cephadm: deploy no more than 5 mons in roleless mode
	qa/tasks/radosbench: default clients to all clients (not client.0)
	qa/tasks/ceph_manager: parallelize flush_pg_stats()
	qa/suites/big: remove thrasher
	qa/suites/big: update for cephadm

Reviewed-by: Sebastian Wagner <sewagner@redhat.com>