start joiner

        Args:
            strPSKd: Joiner's PSKd

        Returns:
            True: successful to start joiner
            False: fail to start joiner

def joinCommissioned(self, strPSKd='threadjpaketest', waitTime=20):
        """start joiner

        Args:
            strPSKd: Joiner's PSKd

        Returns:
            True: successful to start joiner
            False: fail to start joiner
        """
        print '%s call joinCommissioned' % self.port
        self.__sendCommand('ifconfig up')
        cmd = 'joiner start %s %s' %(strPSKd, self.provisioningUrl)
        print cmd
        if self.__sendCommand(cmd)[0] == "Done":
            maxDuration = 150 # seconds
            self.joinCommissionedStatus = self.joinStatus['ongoing']

            if self.logThreadStatus == self.logStatus['stop']:
                self.logThread = ThreadRunner.run(target=self.__readCommissioningLogs, args=(maxDuration,))

            t_end = time.time() + maxDuration
            while time.time() < t_end:
                if self.joinCommissionedStatus == self.joinStatus['succeed']:
                    break
                elif self.joinCommissionedStatus == self.joinStatus['failed']:
                    return False

                time.sleep(1)

            self.__sendCommand('thread start')
            time.sleep(30)
            return True
        else:
            return False