MB-100: some logs in swaprebalance tests

Change-Id: I41e514df40be438bb0b73766d82e2ed5ab0cf5b7
Reviewed-on: http://review.couchbase.org/25285
Reviewed-by: Andrei Baranouski <andrei.baranouski@gmail.com>
Tested-by: Andrei Baranouski <andrei.baranouski@gmail.com>