tests: Make FST config tests more robust and easier to debug
It looks like it is possible for the separate started wpa_supplicant
process to remain running after a test case like fst_sta_config_default.
This would result in failures to run any following test case that uses
the wlan5 interface. Try to kill the process more thoroughly by waiting
for the PID file to show up and write more details into the logs to make
it easier to debug issues in this area.
Signed-off-by: Jouni Malinen <jouni@qca.qualcomm.com>