tests: Work around grpform_pbc_overlap robustness issues
Since P2P Client scan case is now optimzied to use a specific SSID, the
WPS AP will not reply to that and the scan after GO Negotiation can
quite likely miss the AP due to dwell time being short enoguh to miss
the Beaco frame. This has made the test case somewhat pointless, but
keep it here for now with an additional scan to confirm that PBC
detection works if there is a BSS entry for a overlapping AP.
Signed-off-by: Jouni Malinen <j@w1.fi>