node: donwgrade log error to trace for disconnection — heartwood

This is would be a very noisy error since disconnections should be expected to happen frequently for nodes.

Downgrade the log level to trace.

                 log::error!(target: "wire", token=token.0; "Listener disconnected");
             }
             reactor::Error::TransportDisconnect(token, transport) => {
                 log::error!(target: "wire", token=token.0; "Peer disconnected");
                 log::trace!(target: "wire", token=token.0; "Peer disconnected");
                 // We're dropping the TCP connection here.
                 drop(transport);