Currently I'am using Windows 10 Pro Buid 17134.648 and Ubuntu 18.04 within the WSL Bash.
To avoid updating the /etc/resolv.conf wich is a symlink pointing to /run/resolvconf/resolv.conf the default methods like dhclient-enter-hooks.d doesn't work.
Easy way out
Create a new /etc/resolv.conf
Open a regular command prompt (win+r then cmd)
Right-click the title bar and select Properties
Deselect “Use legacy console (requires restart)”