Simplify admin_required policy
Simplify admin_required policy

The admin_required rule as currently defined is equivalent to the
admin_or_cloud_admin rule. If you have the admin role, both wil pass.
If you do not have the admin role, neither will pass. This makes the
policy file simpler and more consistent by removing
admin_or_cloud_admin.

Change-Id: I5c9a96aaf114611ce141f0074ec055ca167c1b63

dims/keystone,openstack/keystone,himanshu-setia/keystone,klmitch/keystone,mahak/keystone,ilay09/keystone,cernops/keystone,mahak/keystone,klmitch/keystone,rajalokan/keystone,rajalokan/keystone,openstack/keystone,himanshu-setia/keystone,ilay09/keystone,rajalokan/keystone,cernops/keystone,mahak/keystone,ilay09/keystone,openstack/keystone,dims/keystone