The test sequence "scan_and_bss_entry_removed ap_wps_ap_scan_2" resulted
in failure due to an old BSS entry remaining from the first test case to
the second and the WPS_PBC operation on a forced BSSID ending up picking
the incorrect BSS entry. Make this more robust by clearing the scan
results from cfg80211.
Signed-off-by: Jouni Malinen <j@w1.fi>