MB-100: fix btc for tests without buckets creation

Change-Id: I4874ef02f987e8f8c4d5a9410e83064dff54a17e
Reviewed-on: http://review.couchbase.org/24732
Tested-by: buildbot <build@couchbase.com>
Reviewed-by: Andrei Baranouski <andrei.baranouski@gmail.com>