Troubleshooting WireGuard connections

[Jason A. Donenfeld]

When you type "wg", does it show you a "latest handshake"? If not,
perhaps they're not even communicating at all. For this, you could
look for udp packets on port 21 and see what's up.

Also, you might simplify things a bit by:
- Removing all mentions of Endpoint on the server, since the server
will learn these from roaming
- Removing all mentions of Port on the clients, since these can be
randomly selected