In the [[ https://github.com/vyos/vyos-replace/blob/e4a2eda8121a3a88b40868996577cde53a34ba0c/files/dhclient-script | /sbin/dhclient-script ]] is still exist $new_interface_mtu part which trying to run:
/opt/vyatta/sbin/vyatta-interfaces.pl --dev=$interface --path
But, this was removed long time ago.
The same situation about vyatta_update_resolv.pl, link to which still exist in dhclient-script, but the script was removed.
We need to remove this rudiments from the dhclient-script too.