Allow to call the discover-latest-image role

It comes from oooq-extras:
https://opendev.org/openstack/tripleo-quickstart-extras/src/branch/master/roles/discover-latest-image

Calling it will allow to correct some issues we may face when the image
changes on a daily basis.

It adds 3 new parameters:
+tripleo_ci_discover_latest (boolean): whether or not discover latest
image
+tripleo_ci_discover_base_url: base_url passed down to the role
+tripleo_ci_discover_qcow_prefix: qcow_prefix passed down to the role

Depends-On: https://review.opendev.org/c/openstack/tripleo-quickstart-extras/+/871833
Change-Id: I89ce291546a68606c1eab1bb9379a21836773c70

roles/oooci-build-images/defaults/main.yaml

@@ -69,3 +69,8 @@ image_sanity_files:
 missing_dirs:
   - /var/lib/pcs
   - /etc/pki/tls/private
+
+# discover-latest-images related params
+tripleo_ci_discover_latest: false
+tripleo_ci_discover_base_url: ''
+tripleo_ci_discover_qcow_prefix: ''

roles/oooci-build-images/tasks/main.yaml

@@ -14,6 +14,26 @@
     path: '{{ workspace }}/logs'
     state: directory
 
+- name: Get the latest image on demand
+  when:
+    - tripleo_ci_discover_latest | bool
+  block:
+    - name: Find latest image name
+      vars:
+        base_url: "{{ tripleo_ci_discover_base_url }}"
+        qcow_prefix: "{{ tripleo_ci_discover_qcow_prefix }}"
+      import_role:
+        name: discover-latest-image
+
+    - name: Set needed facts
+      set_fact:
+        cacheable: true
+        tripleo_image_source: "{{ discovered_image_url }}"
+        baseos_undercloud_image_url: "{{ discovered_image_url }}"
+        baseos_image: "{{ ansible_distribution | lower }}"
+        baseos_image_type: qcow2
+        baseos_md5sum: "{{ discovered_md5sum }} {{ discovered_image_name }}"
+
 - name: Set dib related facts used by tripleo-ci build-image role build template
   set_fact:
     dib_local_image: "{{ workspace }}/{{ tripleo_image_source | urlsplit('path') | basename }}"