Fixed bug on tunnel shutdown when the connection is already down

import socket

from sjrpc.core.protocols import Protocol

from sjrpc.core.exceptions import RpcConnectionError

import pyev

            self._endpoint_reader.stop()

            self._endpoint_writer.stop()

            # Send the end of stream message to the peer:

            try:

                self._connection.rpc.send_special('protoctl', label=self._label, type='eos')

            except RpcConnectionError:

                pass  # Ignore errors when connection is down.

            # Execute the callback:

            self._cb_on_shutdown(self)

            super(TunnelProtocol, self).shutdown()