Closes this IOU VM.

def close(self):
        """
        Closes this IOU VM.
        """

        if not (yield from super().close()):
            return False

        adapters = self._ethernet_adapters + self._serial_adapters
        for adapter in adapters:
            if adapter is not None:
                for nio in adapter.ports.values():
                    if nio and isinstance(nio, NIOUDP):
                        self.manager.port_manager.release_udp_port(nio.lport, self._project)

        yield from self.stop()