Add ZeroMQ test to devstack gate

A ZeroMQ test for devstack gate in addition to
all other checks.

This is a combination ZeroMQ+PostgreSQL check
intended to eventually replace the existing PostgreSQL
test for devstack gating.

Per discussion with jeblair and emonty,
it seems prudent to combine these tests to
minimize testing resource utilization.

Change-Id: I82bc4f2fa3748e2d0a168e5b143df1f7b7f54161
Reviewed-on: https://review.openstack.org/32184
Reviewed-by: James E. Blair <corvus@inaugust.com>
Approved: Clark Boylan <clark.boylan@gmail.com>
Reviewed-by: Clark Boylan <clark.boylan@gmail.com>
Tested-by: Jenkins