Explicitly down Jitsi-Meet containers on upgrade

We've been running into problems with Jitsi-Meet processes not
restarting cleanly if we only docker-compose up after image pulls.
Instead, check for whether the pull resulted in new image downloads
and then cleanly down and up the containers, which seems to address
the problem based on manual testing on the servers.

Change-Id: Id551767e72102a4b8667aa9dacc81755f332a278

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

@@ -84,10 +84,18 @@
   shell:
     cmd: docker-compose pull
     chdir: /etc/jitsi-meet-docker/
-- name: Run docker-compose up
-  shell:
-    cmd: docker-compose up -d
-    chdir: /etc/jitsi-meet-docker/
-- name: Run docker prune to cleanup unneeded images
-  shell:
-    cmd: docker image prune -f
+  register: docker_compose_pull
+- name: Stop/Start containers if needed
+  when: "'downloaded newer image' in docker_compose_pull.stderr"
+  block:
+    - name: Run docker-compose down
+      shell:
+        cmd: docker-compose down
+        chdir: /etc/jitsi-meet-docker/
+    - name: Run docker-compose up
+      shell:
+        cmd: docker-compose up -d
+        chdir: /etc/jitsi-meet-docker/
+    - name: Run docker prune to cleanup unneeded images
+      shell:
+        cmd: docker image prune -f