Switch priority back to critcal on ubuntu preseeds

roles/netbootxyz/templates/menu/ubuntu.ipxe.j2

@@ -62,7 +62,7 @@ goto deb_install
 iseq ${install_type} deb && set install_name preseed ||
 iseq ${install_type} sub && set install_name autoinstall ||
 echo -n Specify ${install_name} URL for ${os} ${ubuntu_version}: && read install_url
-iseq ${install_type} deb && set install_params auto=true priority=low preseed/url=${install_url} ||
+iseq ${install_type} deb && set install_params auto=true priority=critical preseed/url=${install_url} ||
 iseq ${install_type} sub && set install_params autoinstall ds=nocloud-net;s=${install_url} ||
 goto deb_install