CBQE-1512: minor changes in createbuckettests.py

Change-Id: Id368418621e13bfb15aba8e2f85df641c26c91d9
Reviewed-on: http://review.couchbase.org/28299
Tested-by: buildbot <build@couchbase.com>
Reviewed-by: Andrei Baranouski <andrei.baranouski@gmail.com>
Tested-by: Andrei Baranouski <andrei.baranouski@gmail.com>