CI: Reinstate use of Docker registry mirror

After modernising docker configuration
(I1215e04ec15b01c0b43bac8c0e81293f6724f278), we lost our
registry-mirrors configuration in CI that lets us use a mirror of
Dockerhub.

This change uses the new docker_custom_config variable to configure the
registry mirror.

Change-Id: I1430413c12e9d0b59e4f216ff66372de0f3a4f21

tests/run.yml

@@ -12,6 +12,7 @@
         logs_dir: "/tmp/logs"
         kolla_ansible_src_dir: "{{ ansible_env.PWD }}/src/{{ zuul.project.canonical_hostname }}/openstack/kolla-ansible"
         kolla_ansible_local_src_dir: "{{ zuul.executor.work_root }}/src/{{ zuul.project.canonical_hostname }}/openstack/kolla-ansible"
+        infra_dockerhub_mirror: "http://{{ zuul_site_mirror_fqdn }}:8082/"
         need_build_image: false
         build_image_tag: "change_{{ zuul.change | default('none') }}"
         is_upgrade: "{{ 'upgrade' in scenario }}"
@@ -88,12 +89,13 @@
       become: "{{ item.become | default(false) }}"
       vars:
         is_previous_release: "{{ is_upgrade }}"
-        infra_dockerhub_mirror: "http://{{ zuul_site_mirror_fqdn }}:8082/"
       with_items:
         # Docker daemon.json
+        # TODO(mgoddard): Remove templating of docker daemon.json in Ussuri cycle.
         - src: "tests/templates/docker_daemon.json.j2"
           dest: "/etc/docker/daemon.json"
           become: true
+          when: "{{ is_previous_release and previous_release == 'stein' }}"
         # Ansible inventory
         - src: "tests/templates/inventory.j2"
           dest: "{{ kolla_inventory_path }}"

tests/templates/globals-default.j2

@@ -3,6 +3,13 @@ kolla_base_distro: "{{ base_distro }}"
 kolla_install_type: "{{ install_type }}"
 network_interface: "{{ api_interface_name }}"
 docker_restart_policy: "no"
+# TODO(mgoddard): Always do this in Ussuri cycle.
+{% if not is_previous_release or previous_release != 'stein' %}
+docker_custom_config:
+  debug: true
+  registry-mirrors:
+    - {{ infra_dockerhub_mirror }}
+{% endif %}
 
 # Use a random router id, otherwise it may result in the same router id
 # in the CI gate.