Add missing config option os_auth_url

Without this option will appear as an error:
Skip interval_task because Keystone error:
Authorization Failed: Unable to establish connection to
http://localhost:5000/v2.0/tokens

Closes-Bug: #1325383

Change-Id: I42fe92596d9d475f2c5b2a6aa6b49d2b7b821c54
Merge "Add missing config option os_auth_url"