auth: drop service dependency for Keystone_user_role

auth: drop service dependency for Keystone_user_role

Drop service dependency for Keystone_user_role.

Without that patch, Ceilometer & Keystone running in WSGI will fail to compile
the catalog because a dependency cycle:
Anchor[keystone_started] => Keystone_user_role[ceilometer@services] =>
Service[ceilometer-api] => Service[httpd] => Anchor[keystone_started]

The dependency is not really useful because it does not prevent the
service to start.

Change-Id: Id8366cd5d2ddf6da468ecc7adb7d55eb8be4c8d8