test balancer: Backport specific fixes

test balancer: Backport specific fixes

Add "ceph balancer sleep" command to set balancer sleep_interval for testing
Remove unavailable "ceph balancer pool" part of testing
Remove setting of nonexistant osd_pool_default_pg_autoscale_mode
Improve balancer module log message
Fix log message test (no pg merging)
Pool balancing isn't grouped by rule, so results different here

Signed-off-by: David Zafman <dzafman@redhat.com>
(cherry picked from commit 61dedc249bb93a208e685c68a65a5c07d60870d1)
	From mimic backport