fix(systemd): lookup default gateway interface for HOST_IP

- only pull images if they don't already exist in the local docker cache

Author: Gabriel Monroy

systemd/deis-controller.service

@@ -3,8 +3,8 @@ Description=deis-controller
 
 [Service]
 TimeoutStartSec=20m
-ExecStartPre=/usr/bin/docker pull deis/controller
-ExecStart=/bin/sh -c "HOST_IP=$(/bin/ifconfig eth0 | awk '/inet /{print $2}') && exec /usr/bin/docker run --name deis-controller -p 8000:8000 -e PUBLISH=8000 -e HOST=$HOST_IP deis/controller"
+ExecStartPre=/bin/sh -c "/usr/bin/docker history deis/controller >/dev/null || /usr/bin/docker pull deis/controller"
+ExecStart=/bin/sh -c "IFACE=$(netstat -nr | grep ^0.0.0.0 | awk '{print $8}') && HOST_IP=$(/bin/ifconfig $IFACE | awk '/inet /{print $2}') && exec /usr/bin/docker run --name deis-controller -p 8000:8000 -e PUBLISH=8000 -e HOST=$HOST_IP deis/controller"
 ExecStop=/usr/bin/docker rm -f deis-controller
 
 [Install]