Use Keystone internal endpoint instead of admin for services

Use Keystone internal endpoint instead of admin for services

The admin endpoint is listening on the ctlplane network by default;
services should ideally be using the internal api network for this kind
of traffic, as the ctlplane network is mostly for provisioning. On the
other hand, the admin endpoint shouldn't be as relevant with services
switching to keystone v3.

Change-Id: I1213a83ef8693c1cca1d20de974f7949a801d9f1