Closes this cloud.

def close(self):
        """
        Closes this cloud.
        """

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

        for nio in self._nios.values():
            if nio and isinstance(nio, NIOUDP):
                self.manager.port_manager.release_udp_port(nio.lport, self._project)

        yield from self._stop_ubridge()
        log.info('Cloud "{name}" [{id}] has been closed'.format(name=self._name, id=self._id))