update for machine-id

newer versions will automatically populate an empty /etc/machine-id

prepare-ubuntu-18.04-template.sh

@@ -80,8 +80,9 @@ truncate -s0 /etc/hostname
 hostnamectl set-hostname localhost
 
 #remove machine-id
-rm /etc/machine-id
-rm /var/lib/dbus/machine-id
+#rm /etc/machine-id
+#rm /var/lib/dbus/machine-id
+echo -n > /etc/machine-id
 
 #cleanup apt
 apt clean