MB-100: more logs in upgrade tests

Change-Id: I81337a67531064d9d33af43d517a066b50841af8
Reviewed-on: http://review.couchbase.org/25283
Reviewed-by: Andrei Baranouski <andrei.baranouski@gmail.com>
Tested-by: Andrei Baranouski <andrei.baranouski@gmail.com>