Removing rbac_roles from config.py.

This option was needed for the old rbac converter framework.
Now, rbac_roles is no longer needed so has been removed.

The recent framework changes were made in this commit:
https://review.openstack.org/#/c/424347/

Change-Id: I69f9a2f4e39ed733f12253aba49f32c3c70b7b3a
3 files changed