Enable quantum-ovs-cleanup service where it exists

Red Hat-based distros have a service which calls the
quantum-ovs-cleanup binary when appropriate. It doesn't appear that
non-Red Hat-based distros have this service.

Change-Id: I8050127265450014815813ef3c56126252e6feac
Add support for auth_admin_prefix for auth_token

Add support for auth_admin_prefix in the keystone
auth_token configuration of quantum::server.

Change-Id: I3d46dd4313b02115f690157ea169a5eee0aba513
Ensure ovs-cleanup service started after it is installed

Change-Id: Ie26b8c124c03b219307c3e5effba4f67b8148914
Creates external bridge before starting ovs agent

The agent is currently involved in a race condition
where br-ex is created after it, but will still be
created before the agent searches for it in cases
where the intermediate resources are resolved quickly.

The agent will terminate immediately if the bridge
is not found.

Change-Id: Ie93289ce156f5c1d76bae7616b573107d16dd6aa
Fixes: bug #1190117
Merge "Add support for auth_admin_prefix for auth_token"