Comment 1 for bug 1813164

The nameserver is provided at runtime by the local DHCP server, these are not coded in the image. These are being injected by the infrastructure where your vagrant box is running. The code which creates this image is available for inspection @ https://git.launchpad.net/ubuntu/+source/livecd-rootfs/tree/live-build/ubuntu-cpc/hooks/042-vagrant.binary?h=ubuntu/bionic-devel

Sorry to hear that your provider is doing this, it is frustrating. I'm going to close this as invalid as the image itself is not the source of this unfortunate behavior.