rm-cluster should call `ceph mgr module disable cephadm`

[sebastian-philipp]

ceph-salt/ceph-salt-formula/salt/_states/ceph_orch.py

Lines 108 to 110 in 4f44d1b

	__salt__['ceph_salt.begin_stage']("Remove cluster {}".format(fsid))
	cmd_ret = __salt__['cmd.run_all']("cephadm rm-cluster --fsid {} "
	"--force".format(fsid))

compare that to

• cephadm-purge: disable cephadm before purging cephadm-ansible#50
• doc/cephadm: fixing cluster purging section ceph#44810