fix: peer connect panic on log

[garyyu]

Two reports in Gitter lobby on this panic error:

thread 'peer_connect' panicked at 'called `Result::unwrap()` on an `Err` value: Os { code: 107, kind: NotConnected, message: "Transport endpoint is not connected" }': libcore/result.rs:1009stack backtrace:

I got the log file and find 97 such panic errors in 24 hours.

I guess the related code is:

		debug!("connect: handshaking with {:?}", conn.peer_addr().unwrap());

which is just imported in a recent PR.

So, let's remove that unwrap().