Improve docker support

Some general cleanup, and added support for more docker service configuration.  This allows things like [tes/infra-skydns bosco-service.json](/tes/infra-skydns/blob/master/bosco-service.json) and [tes/infra-skydock bosco-service.json](/tes/infra-skydock/blob/master/bosco-service.json) .