Flesh out and test INET6

[rennergade]

We haven't fully tested INET6 sockets and currently don't register INET6 addresses to our net devices file. We should be able to modify gen_netdevs to add ipv6 addresses, and then we can robustly test networking calls with this kind of socket.

[davidge20]

Currently, while the server supports IPv6 addresses, our containers do not. We need to enable IPv6 support on docker containers.

More details on how to do that are here: https://docs.docker.com/config/daemon/ipv6/