power up the Thread device

def powerUp(self):
        """power up the Thread device"""
        print '%s call powerUp' % self.port
        if not self.handle:
            self._connect()

        self.isPowerDown = False
        if self.__sendCommand(WPANCTL_CMD + 'attach')[0] != 'Fail':
            time.sleep(3)
        else:
            return False

        if self.__sendCommand(WPANCTL_CMD + 'setprop Daemon:AutoAssociateAfterReset true')[0] == 'Fail':
            return False

        if self.__stripValue(self.__sendCommand(WPANCTL_CMD + 'getprop -v NCP:State')[0]) != 'associated':
            print 'powerUp failed'
            return False
        else:
            return True