scantest.c works only once until reboot Beaglebone

The first time I ran the scantest.c, the BLE devices are detected successfully. However, I have to reboot the Beaglebone to have the st work again.

[wunnation]

I ran into a similar issue with the C.H.I.P.

In my experience, it only happens when program does not shut down properly.
If you press 'q' in the terminal where you are running the application, the program shut down the hci link properly, and you can run it again.

[chenxiaosonggithub]

Before run the scan test, if the scan state is enabled, you should disable the scan state, then you can set the scan parameters.