Avoid oslo.messaging 1.5.0

1.5.0 dropped the fake_rabbit option which was still used by some
projects.  It was reintroduced in 1.5.1.

Change-Id: I47138da02c58073b03e3fb40537cc6f0b6a94a3c
Related-bug: #1399085
(cherry picked from commit c13842a06f2bcce7e65292ac75e0d6f44af08255)