Use localPort option during TCP connect

[achingbrain]

For autoNAT to work correctly, we should use the localPort option in socket.connect to ensure we use a predictable port. Otherwise we end up using ephemeral ports and each autoNAT interaction tries to confirm a different port number.

[achingbrain]

I think for this to work we need to be able to open ports with SO_REUSEPORT. This is not currently supported by node.js but it appears to have made it in to libuv so that may change in a future release.

Other reading:

• https://stackoverflow.com/questions/14388706/how-do-so-reuseaddr-and-so-reuseport-differ/14388707#14388707
• https://man7.org/linux/man-pages/man7/socket.7.html