roles/docker: Install and set up Docker daemon

The *docker* role configures the Docker daemon on the managed machine.

roles/docker/templates/daemon.json.j2

@@ -0,0 +1,16 @@
+{
+{% if docker_enable_tls %}
+    "tls": true,
+    "tlscert": "/etc/pki/tls/certs/docker.cer",
+    "tlskey": "/etc/pki/tls/private/docker.key",
+    "tlsverify": true,
+    "tlscacert": "/etc/pki/tls/certs/docker-ca.crt",
+    "hosts": [
+{% if docker_allow_outside %}
+        "tcp://[::]:{{ docker_listen_port }}",
+{% endif %}
+        "unix:///var/run/docker.sock"
+    ],
+{% endif %}
+    "log-level": "{{ docker_log_level }}"
+}