Add convenient method to get admin role

[Kenji Ishii]

Method which get admin roles is needed not only openstack-auth but also Horizon.
In addition, the format of "openstack.roles.xxxx" is defined in openstack-auth.
Therefore, convenient method which written on above should be defined on openstack_auth.

ref
https://bugs.launchpad.net/horizon/+bug/1534409
https://review.openstack.org/#/c/268899/

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/271198

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/271198
Committed: https://git.openstack.org/cgit/openstack/django_openstack_auth/commit/?id=d779eb6fe3dedcd37e777f1530fa24a1a9343353
Submitter: Jenkins
Branch: master

commit d779eb6fe3dedcd37e777f1530fa24a1a9343353
Author: Kenji Ishii <email address hidden>
Date: Fri Jan 22 18:17:37 2016 +0900

    Add convenient method to get admin roles and permissions

    admin roles and admin permissions (like 'openstack.roles.xxxx')
    depends on OPENSTACK_KEYSTONE_ADMIN_ROLES.
    These information is needed with openstack_auth and Horizon at least
    as common information.
    So, this patch provide these methods as a convenient method at
    openstack_auth.

    Change-Id: Idad1860684b1e772fc31f16fc8c0263e49fc3919
    Closes-Bug: #1536896

[Doug Hellmann (doug-hellmann)]

This issue was fixed in the openstack/django_openstack_auth 2.2.0 release.