For debian-only image don't add a motd

src/freedombone-image-customise

@@ -124,6 +124,10 @@ EOF
 }
 
 configure_networking() {
+    if [[ $DEBIAN_INSTALL_ONLY != "no" ]]; then
+        return
+    fi
+    
     if [[ $GENERIC_IMAGE == "no" ]]; then
         echo "# This file describes the network interfaces available on your system
 # and how to activate them. For more information, see interfaces(5).