split network plugins into distinct roles

roles/network_plugin/flannel/templates/systemd-docker.service

@@ -0,0 +1,28 @@
+[Unit]
+Description=Docker Application Container Engine
+Documentation=http://docs.docker.com
+{% if ansible_os_family == "RedHat" %}
+After=network.target
+Wants=docker-storage-setup.service
+{% elif ansible_os_family == "Debian" %}
+After=network.target docker.socket
+Requires=docker.socket
+{% endif %}
+
+[Service]
+Type=notify
+EnvironmentFile=-/etc/default/docker
+Environment=GOTRACEBACK=crash
+ExecStart=/usr/bin/docker daemon \
+          $OPTIONS \
+          $DOCKER_STORAGE_OPTIONS \
+          $DOCKER_NETWORK_OPTIONS \
+          $INSECURE_REGISTRY
+LimitNOFILE=1048576
+LimitNPROC=1048576
+LimitCORE=infinity
+MountFlags=slave
+TimeoutStartSec=1min
+
+[Install]
+WantedBy=multi-user.target