Restore old task for docker-daemon.json

This code:
  {% if container_registry_mirrors | length > 0 %}registry-mirrors: [{{ container_registry_mirrors }}]{% endif %}

Needs to include the brackets and I haven't found a way yet to include
them without Ansible failure. In the meantime, let's go back on the old
code.

defaults/main.yml

@@ -10,5 +10,5 @@ container_registry_insecure_registries: []
 container_registry_network_options: ''
 container_registry_host: localhost
 container_registry_port: 8787
-container_registry_mirrors: []
+container_registry_mirror: ''
 container_registry_storage_options: '-s overlay2'

tasks/docker.yml

@@ -50,8 +50,8 @@
     registry_flags: "{% for reg in container_registry_insecure_registries %}--insecure-registry {{ reg }}{% if not loop.last %} {% endif %}{% endfor %}"
 
 - name: manage /etc/docker/daemon.json
-  copy:
-    content: "{{ _docker_daemon_config | from_yaml | to_nice_json }}"
+  template:
+    src: docker-daemon.json.j2
     dest: /etc/docker/daemon.json
   notify: restart docker service
 

templates/docker-daemon.json.j2

@@ -0,0 +1,6 @@
+{
+{% if container_registry_mirror != "" %}
+  "registry-mirrors": ["{{ container_registry_mirror }}"],
+{% endif %}
+  "debug": {{ container_registry_debug|lower }}
+}

vars/main.yml

@@ -1,4 +1 @@
 _full_docker_options: "{% if ansible_selinux.status == 'enabled' %}--selinux-enabled {% endif %}{{ container_registry_docker_options }}"
-_docker_daemon_config: |
-  debug: {{ container_registry_debug }}
-  {% if container_registry_mirrors | length > 0 %}registry-mirrors: [{{ container_registry_mirrors }}]{% endif %}