The keystone documentation highly recommends disabling the admin_token
authentication after the initial bootstrap because it exposes a major
attack vector.
A patch in puppet-keystone [1] added the support to remove
admin_token_auth keyword from the pipeline lists.
This patch aims to use this new class when deploying Keystone.
[1] https://review.openstack.org/#/c/256248
Change-Id: Ic545005122a0f7b92b8a9d3f1e4978b397bfc9c2