Refactor check for new container images

Two of our services (gitea and jitsi meet) need to take special action
when docker-compose pull updates images and cannot rely on a basic up -d
after a pull. Previously we checked the stderr output of docker-compose
for a string indicating at least one image was updated to determine if
any images updated. The problem with this approach is docker compose is
less verbose than docker-compose and does not give us this information.

In preparation for our slow but eventual migration to docker compose for
these services update the new image check process. Now we perform a
docker image listing before and after the pull and compare the emitted
image ID lists. Image ids should change when we pull new images and
their sort order should be stable command to command (they are sorted by
image age).

Change-Id: I7e9ca8cc7bc0454dcca82c02b6913d81aa4927b3

playbooks/roles/gitea/tasks/main.yaml

@@ -41,14 +41,23 @@
 - name: Install reverse proxy
   include_tasks: proxy.yaml
 
+- name: Get list of image IDs pre pull
+  # The --quiet flag prints out only image IDs
+  command: docker image list --quiet
+  register: pre_pull_image_ids
+
 - name: Run docker-compose pull
   shell:
     cmd: docker-compose pull
     chdir: /etc/gitea-docker/
-  register: docker_compose_pull
+
+- name: Get list of image IDs post pull
+  # The --quiet flag prints out only image IDs
+  command: docker image list --quiet
+  register: post_pull_image_ids
 
 - name: Stop/Start gitea safely for Gerrit replication
-  when: "'downloaded newer image' in docker_compose_pull.stderr"
+  when: pre_pull_image_ids.stdout_lines|sort != post_pull_image_ids.stdout_lines|sort
   block:
     - name: Run docker-compose stop
       shell:

playbooks/roles/jitsi-meet/tasks/main.yaml

@@ -80,13 +80,23 @@
       yes
     creates: /var/jitsi-meet/jvb/jvb-keystore.store
 
+- name: Get list of image IDs pre pull
+  # The --quiet flag prints out only image IDs
+  command: docker image list --quiet
+  register: pre_pull_image_ids
+
 - name: Run docker-compose pull
   shell:
     cmd: docker-compose pull
     chdir: /etc/jitsi-meet-docker/
-  register: docker_compose_pull
+
+- name: Get list of image IDs post pull
+  # The --quiet flag prints out only image IDs
+  command: docker image list --quiet
+  register: post_pull_image_ids
+
 - name: Stop/Start containers if needed
-  when: "'downloaded newer image' in docker_compose_pull.stderr"
+  when: pre_pull_image_ids.stdout_lines|sort != post_pull_image_ids.stdout_lines|sort
   block:
     - name: Run docker-compose down
       shell: