Add special case for WSL 2 during enable-ipv6

[steersbob]

Docker Desktop with a WSL2 backend does not store daemon settings in /etc/docker, and does not pass a --config argument to dockerd.

Actual daemon.json file can be edited through the UI or found in %USERPROFILE%/.docker/

It's unclear whether the IPv6 fix is required for WSL2 backends.

https://stackoverflow.com/questions/38086185/how-to-check-if-a-program-is-run-in-bash-on-ubuntu-on-windows-and-not-just-plain