Honor keystone policy file when creating client

When creating the keystone client for an admin the user is checked
for the specific role of "admin" to determine if they are authorized
to use the admin URL. This patch changes this logic so that the
policy file is honored instead of a specific role.

Closes-Bug: #1336418
Change-Id: I600334dff17a5564f97cbcce67ff6d3619142961
Merge "Honor keystone policy file when creating client"