ignore dropped connections

[seunlanlege]

Previously If there's no peer_addr on the socket, this causes the tcp-server to panic.

jsonrpc/tcp/src/server.rs

Lines 87 to 93 in 4418476

	let listener = tokio::net::TcpListener::bind(&address)?;
	let connections = SuspendableStream::new(listener.incoming());
	let server = connections.map(move |socket| {
	let peer_addr = socket.peer_addr().expect("Unable to determine socket peer address");
	trace!(target: "tcp", "Accepted incoming connection from {}", &peer_addr);
	let (sender, receiver) = mpsc::channel(65536);

Instead of panicking this PR instead ignores the connection as it has most likely been dropped by the client.

closes #500

[dvdplm]

PR description please?

[dvdplm]

lgtm but a test would be nice.

[dvdplm]

Suggested change

	trace!(target: "tcp", "Unable to determine socket peer address, ignoring connection {}", e);
	warn!(target: "tcp", "Unable to determine socket peer address, ignoring connection {}", e);

[niklasad1]

@seunlanlege after this gets merged please update the version number and release a new version on crates.io so we can use it in parity-ethereum

[tomusdrw]

lgtm, just address David's grumble.