Prune docker images after docker-compose up

This ensures that we cleanup images that are superceded and no longer
necessary. We do this to avoid filling the disk with docker images.

Note that we use the -f flag to avoid being prompted by docker image
prune for confirmation.

Change-Id: I8eb5bb97d8c66755e695498707220c9e6e7b2de0

playbooks/roles/gitea/tasks/main.yaml

@@ -45,6 +45,9 @@
   shell:
     cmd: docker-compose up -d --timeout 60
     chdir: /etc/gitea-docker/
+- name: Run docker prune to cleanup unneeded images
+  shell:
+    cmd: docker image prune -f
 - name: Check if root user exists
   uri:
     url: "https://localhost:3000/api/v1/users/root"

playbooks/roles/haproxy/tasks/main.yaml

@@ -28,3 +28,6 @@
   shell:
     cmd: docker-compose up -d
     chdir: /etc/haproxy-docker/
+- name: Run docker prune to cleanup unneeded images
+  shell:
+    cmd: docker image prune -f

playbooks/roles/registry/tasks/main.yaml

@@ -49,6 +49,9 @@
   shell:
     cmd: docker-compose up -d
     chdir: /etc/registry-docker/
+- name: Run docker prune to cleanup unneeded images
+  shell:
+    cmd: docker image prune -f
 
 - name: Install cron to garbage collect the registry daily
   cron:

playbooks/roles/zuul-preview/tasks/main.yaml

@@ -15,3 +15,6 @@
   shell:
     cmd: docker-compose up -d
     chdir: /etc/zuul-preview-docker/
+- name: Run docker prune to cleanup unneeded images
+  shell:
+    cmd: docker image prune -f