Add support for django_openstack_auth

It would be useful for development, reviewing and testing to add
support for django_openstack_auth to devstack.

This change adds the integration tests to the openstack_auth
list of test: https://review.openstack.org/#/c/86528/

Change-Id: Ifbd336b83f6b2beb23996b599ec820232c13efdd
Closes-Bug: #1262121
Merge "Add support for django_openstack_auth"