fix(docker): add an ARP entry each time a container comes up

Author: mboersma

controller/scheduler/coreos.py

@@ -212,6 +212,8 @@ def attach(self, name):
 [Service]
 ExecStartPre=/usr/bin/docker pull {image}
 ExecStart=-/usr/bin/docker run --name {name} -P -e PORT={port} {image} {command}
+ExecStartPost=-/bin/sh -c "until docker inspect {name} >/dev/null 2>&1; do sleep 1; done"; \
+    -/bin/sh -c "arping -Idocker0 -c1 `docker inspect -f '{{{{ .NetworkSettings.IPAddress }}}}' {name}`"
 ExecStop=-/usr/bin/docker rm -f {name}
 """