Add gitdm to openstack infrastructure.

Change-Id: Id19133976c2e4013655a88637cb241c18d67e5bb
Reviewed-on: https://review.openstack.org/27425
Reviewed-by: Jeremy Stanley <fungi@yuggoth.org>
Reviewed-by: Anita Kuno <anita.kuno@enovance.com>
Reviewed-by: Clark Boylan <clark.boylan@gmail.com>
Approved: James E. Blair <corvus@inaugust.com>
Reviewed-by: James E. Blair <corvus@inaugust.com>
Tested-by: Jenkins