Close the link.

def close(self):
        """ Close the link. """
        # Stop the comm thread
        self._thread.stop()

        # Close the USB dongle
        try:
            if self.cfusb:
                self.cfusb.set_crtp_to_usb(False)
                self.cfusb.close()
        except Exception as e:
            # If we pull out the dongle we will not make this call
            logger.info('Could not close {}'.format(e))
            pass
        self.cfusb = None