Use consistent role schema in token response validation
Use consistent role schema in token response validation

The tests used a different schema for the roles in the token
response schema for different token scopes. The role information
shouldn't change depending on the scope, so let's make the test
more DRY by not redefining the role schema in multiple places.

Related-Bug: 1763510
Change-Id: I58d3dc2a3306994890688d5ff40a62cdaedf378e

mahak/keystone,mahak/keystone,mahak/keystone,openstack/keystone,openstack/keystone,openstack/keystone