Collect docker logs in functional test

If any containers are still running at the end of the test,
collect their logs.

Change-Id: I9d667e646f2a37a63bf6c311b511e567bb3f153c

.zuul.yaml

@@ -21,6 +21,7 @@
     parent: opendev-build-docker-image
     allowed-projects: zuul/zuul-registry
     run: playbooks/functional-test/run.yaml
+    post-run: playbooks/functional-test/post.yaml
     vars: &image_vars
       docker_images:
         - context: .
@@ -33,6 +34,7 @@
     description: Build and test a Docker image and upload to Docker Hub.
     allowed-projects: zuul/zuul-registry
     run: playbooks/functional-test/run.yaml
+    post-run: playbooks/functional-test/post.yaml
     secrets:
       name: docker_credentials
       secret: zuul-registry-dockerhub

playbooks/functional-test/post.yaml

@@ -0,0 +1,17 @@
+- hosts: all
+  tasks:
+    - name: List containers
+      command: "docker ps -a --format '{{ '{{ .Names }}' }}'"
+      register: docker_containers
+      ignore_errors: true
+
+    - name: Create container log dir
+      file:
+        path: "{{ ansible_user_dir }}/zuul-output/logs/docker"
+        state: directory
+
+    - name: Save container logs
+      loop: "{{ docker_containers.stdout_lines | default([]) }}"
+      shell: "docker logs {{ item }} &> {{ ansible_user_dir }}/zuul-output/logs/docker/{{ item }}.txt"
+      args:
+        executable: /bin/bash