I'm not sure why you think retrieving domain info from the DHCP server will do anything to help the problem, which is that the Ubuntu DHCP client is overwriting the resolv.conf file and replacing nameservers that were added due to VPN connections.
I'm not sure why you think retrieving domain info from the DHCP server will do anything to help the problem, which is that the Ubuntu DHCP client is overwriting the resolv.conf file and replacing nameservers that were added due to VPN connections.