MB-100: more logs in wait_for_failover_or_assert

Change-Id: I6ba4462ee612c3e1b87c4138443ed24ae995a482
Reviewed-on: http://review.couchbase.org/24657
Tested-by: buildbot <build@couchbase.com>
Reviewed-by: Andrei Baranouski <andrei.baranouski@gmail.com>