Add more information to the service catalogs to enable federated zones.

At their most abstract, zones are a meta-concept layered over independent installations of OpenStack services. Whether nova cells, or swift regions, whatever quantum calls them, or federated instances of glance, a base zone need not be aware of the infrastructure, data, or implementation of their peers. After authenticating with Keystone, you receive back a service catalog containing the end-points for each service. Since we return endpoints in a list, we already expose a way of handling zones in a simple, effective manner.