Updated openstack/openstack
Project: openstack-dev/devstack  7c5a02c48c253c592069d7dbe405a50ed76efa4b

Add optional repo enablement for RHEL 7

The RHEL 7 and RHEL 6 optional repos have different names. This enables
the correct repo depending on the release.

Change-Id: I6772c9903a5b9e98cb870d586629564126a6119a