Always register api.domain with the router

* api.domain will always reach the cloud controller.
* Any existing prefixes will also be registered so they will work too.
* Manifests that use ccng will continue to work with both ccng.domain and
api.domain with no changes.

* NOTICE: merge this commit after bump the ccng commit with the same name.

https://github.com/cloudfoundry/cloud_controller_ng/pull/34