meta-iotqa:fix stability problem of wifi connection case
meta-iotqa:fix stability problem of wifi connection case

Sometimes (~40% possibility) the wifi scan will fail to search out all nearby
services, then wifi connection case will not pass. Add 1 time retry to scan,
it will help to improve stability.

Related-to bug fix: none

Signed-off-by: Zhang Jingke <0979c04a6d09a3b3c8dd699e3664fb112fdd2a5b@intel.com>

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