Run pbr integration after running devstack.

We need to run devstack to get some of the dev depends installed.

Change-Id: I57087797b6040ddcf625165a58184d89c65b04f5
Reviewed-on: https://review.openstack.org/33878
Reviewed-by: Jeremy Stanley <fungi@yuggoth.org>
Approved: Clark Boylan <clark.boylan@gmail.com>
Reviewed-by: Clark Boylan <clark.boylan@gmail.com>
Tested-by: Jenkins