add local-only host portmapping for urbit

docker/urbit.go

@@ -105,6 +105,7 @@ func urbitContainerConf(containerName string) (container.Config, container.HostC
 	} else {
 		devMode = "False"
 	}
+	// construct the network configuration based on conf val
 	var httpPort string
 	var amesPort string
 	var network string