Replace -g with --data-root

packer/riju-init-volume

@@ -55,7 +55,7 @@ mount -a
 
 print "filesystem mounted at ${mount_point}"
 
-docker_args="-g ${mount_point}/docker"
+docker_args="--data-root ${mount_point}/docker"
 
 if ! cat /lib/systemd/system/docker.service | grep -q -- "${docker_args}"; then
     print "adding '${docker_args}' to docker.service"