update mraa_hello using os.path.dirname() to get the test file
update mraa_hello using os.path.dirname() to get the test file

daweiwu/meta-iotqa-1,ostroproject/meta-iotqa,daweiwu/meta-iotqa-1,daweiwu/meta-iotqa-1,ostroproject/meta-iotqa,wanghongjuan/meta-iotqa-1,ostroproject/meta-iotqa,daweiwu/meta-iotqa-1,wanghongjuan/meta-iotqa-1,daweiwu/meta-iotqa-1,ostroproject/meta-iotqa,wanghongjuan/meta-iotqa-1,ostroproject/meta-iotqa,wanghongjuan/meta-iotqa-1,wanghongjuan/meta-iotqa-1