Liberty Release CI Updates

* Run the devstack job against changes to ``akanda-appliance`` or
  ``akanda-appliace-builder`` with a configuration such that the appliance
  image will be built from source including the patch under review: DONE
   - Addressed by: https://review.openstack.org/#/c/182391/

* Run the devstack job against all other relevant akanda repositories with a
  configuration such that a pre-built appliance image from a known location on
  the internet. Ideally, this will be the image produced from changes to
  the appliance repositories (ie, akanda-appliance-latest.qcow2): DONE
   - Addressed by: https://review.openstack.org/#/c/182391/

* Setup doc build hooks for all projects and readthedocs.org: DONE
  - Addressed by: https://review.openstack.org/188909

* Setup infrastructure to publish a new appliance image
  (ie, akanda-appliance-latest.qcow2) to a known location on the internet
  after code lands in ``akanda-appliance`` or ``akanda-appliance-builder``: INPROGRESS

Gerrit topic: https://review.openstack.org/#q,topic:bp/liberty-ci-updates,n,z

Addressed by: https://review.openstack.org/194825
    remove stale appliance-builder content