The only instance of `seed-docker-images.service` is inside `contrib/coreos/user-data`. I guess that means that `contrib/rackspace` and `contrib/ec2` should be using this user-data file? Not sure if I can point to one in a CloudFormation template, as it's [built into the template](https://github.com/opdemand/deis/blob/master/contrib/ec2/deis.template#L174-L185).