Add new hiera agent hook to overcloud images.
Add new hiera agent hook to overcloud images.

This patch adds the package for the new heat agent hiera hook
to the overcloud image. This is a move towards helping us optimize the
way Hiera is configured on the overcloud nodes.

Depends-On: I21639f6aadabf9e49f40d1bb0b1d0edcfc4dbc5e

Change-Id: Ia1864933235152b7e899c4442534879f8e22240d
Partial-bug: #1596373

openstack/tripleo-common,openstack/tripleo-common