overcloud admin authorize can no longer be used with
ephemeral Heat. This change allows us to use an existing
inventory file. It also allows for the use to provide a
group from the Inventory rather than running against all
of the nodes in the inventory.
Change-Id: I07902a84e16af94b250ecb621017cd5b7de40a9c
(cherry picked from commit a2b6a9addd)