Add After=mariadb.service postgresql.service rabbitmq-server.service

Adding theses lines to the systemd .service files will help to order
the boot/shutdown process when the database and/or RabbitMQ are
running on the same node as the service.

Also done:
- for glance-api, explicitly call glance-manage with config-dir to be
  able to add config snippets to /etc/glance/glance-api.conf.d/
- Drop some empty lines in the .service files

Change-Id: Id9c36226289304adb7ef2438f6bc2de1dde9e144

openstack/neutron-vpnaas/openstack-neutron-vyatta-agent.service

@@ -1,6 +1,7 @@
 [Unit]
 Description=Neutron VPN as a Service - Brocade Vyatte agent
 After=syslog.target network.target
+After=mariadb.service postgresql.service rabbitmq-server.service
 
 [Service]
 Type=simple