CBQE-0: getting rid of spams in test_progress_rebalance_in log

Change-Id: Id3b042b3cb12be0c5f21f52e7dc6321fdd048dc7
Reviewed-on: http://review.couchbase.org/34329
Tested-by: buildbot <build@couchbase.com>
Reviewed-by: Andrei Baranouski <andrei.baranouski@gmail.com>