Fix swift client token authentication

Fix swift client token authentication

Triggered by launching a stack containing swift containers
through Horizon.

The swift client does its own endpoint lookup if we don't know
it, so we don't have to do it ourselves. Also, our endpoint lookup
was broken in the auth_token codepath.

Part of blueprint auth-token-only

Change-Id: I1876f233001a58cb17e7dd7d5cf8883e295a9b87