Fixed bug with shutdown on RpcProtocol.

    def shutdown(self):

        # Release all waiting calls from this rpc:

        for cid, call in self._calls.iteritems():

        for cid in self._calls:

            err = {'exception': 'RpcError',

                   'message': 'Connection reset by peer'}

            if 'event' in call:

                call['error'] = err

                call['return'] = None

                call['event'].set()

            else:

                msg = {'id': cid, 'error': err, 'return': None}

                self._manager.signal_arrival(msg)

            self._handle_response({'id': cid, 'return': None, 'error': err})

        # Execute on_disconnect callback:

        callback = None