stop commissioner

        Returns:
            True: successful to stop commissioner
            False: fail to stop commissioner

def commissionerUnregister(self):
        """stop commissioner

        Returns:
            True: successful to stop commissioner
            False: fail to stop commissioner
        """
        print '%s call commissionerUnregister' % self.port
        cmd = 'commissioner stop'
        print cmd
        return self.__sendCommand(cmd)[0] == 'Done'