Implement standardised Ubuntu Cloud Archive repo vars

This patch implemented the vars for UCA which are present in the
os_nova and ceph_client roles in order to improve consistency and
easier overriding of any of the chosen parts.

The tasks implementing the UCA configuration are also slightly
adjusted to be a little more robust and complete.

Change-Id: I5ab9238245932de7f3ffc07ffe52725616f4f637

tasks/ovs_install-apt.yml

@@ -13,20 +13,23 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-- name: Add Ubuntu Cloud Archive Keyring package
+- name: Add Ubuntu Cloud Archive keyring
   apt:
     pkg: ubuntu-cloud-keyring
-  register: add_keys
+    state: latest
+  register: add_uca_keys
 
-- name: Enable OVS repo
+- name: Add Ubuntu Cloud Archive Repository
   apt_repository:
-    repo: "{{ ovs_apt_repo }}"
+    repo: "{{ uca_repo }}"
     state: present
+  register: add_uca_repo
 
-- name: Update apt after OVS repo
+- name: Update apt cache after repo addition
   apt:
     update_cache: yes
-  when: add_keys.changed
+  when: add_uca_keys | changed or
+        add_uca_repo | changed
 
 - name: Install apt packages
   apt:

vars/ubuntu-14.04.yml

@@ -13,7 +13,12 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-ovs_apt_repo: 'deb http://ubuntu-cloud.archive.canonical.com/ubuntu trusty-updates/mitaka main'
+# There are no UCA packages for Trusty beyond Mitaka, so the selected
+# release here has to remain at Mitaka.
+uca_openstack_release: mitaka
+uca_apt_repo_url: "http://ubuntu-cloud.archive.canonical.com/ubuntu"
+uca_repo_dist: "{{ ansible_lsb.codename }}-updates/{{ uca_openstack_release }}"
+uca_repo: "deb {{ uca_apt_repo_url }} {{ uca_repo_dist }} main"
 
 ovs_apt_packages:
   - openvswitch-common

vars/ubuntu-16.04.yml

@@ -13,9 +13,10 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-# This has to be reworked because openvswitch packages are not part of the UCA now
-# current version is included in mainstream xenial.
-ovs_apt_repo: 'deb http://ubuntu-cloud.archive.canonical.com/ubuntu xenial-updates/newton main'
+uca_openstack_release: newton
+uca_apt_repo_url: "http://ubuntu-cloud.archive.canonical.com/ubuntu"
+uca_repo_dist: "{{ ansible_lsb.codename }}-updates/{{ uca_openstack_release }}"
+uca_repo: "deb {{ uca_apt_repo_url }} {{ uca_repo_dist }} main"
 
 ovs_apt_packages:
   - openvswitch-common