Add extra test coverage for unscoped token invalidation

As noted in review https://review.openstack.org/#/c/46972/ - this is
just adding a "missing" one-liner to make the test coverage symmetrical.

Related-Bug: 1226225
Change-Id: I6f008a149cc428fcbb023dd9daa0dae0db53aeac
Merge "Add extra test coverage for unscoped token invalidation"