P2P: Fix p2p_connect join scan handler in error cases

wpa_drv_scan() may fail for the initial p2p_connect join scan request,
e.g., if the driver happened to be scanning at the time the new
operation was initialized. Previously, a special scan result handler was
registered regardless of whether the new scan was started. This could
result in partial scan results (e.g., from p2p_find social scan) from
being used as full results for join (or now more importantly for
p2p_connect auto) purposes. Fix this by registering the new scan result
handler only if wpa_drv_scan() returns success.

Signed-hostap: Jouni Malinen <jouni@qca.qualcomm.com>

wpa_supplicant/p2p_supplicant.c

@@ -2863,8 +2863,9 @@ static void wpas_p2p_join_scan(void *eloop_ctx, void *timeout_ctx)
 	 * Run a scan to update BSS table and start Provision Discovery once
 	 * the new scan results become available.
 	 */
-	wpa_s->scan_res_handler = wpas_p2p_scan_res_join;
 	ret = wpa_drv_scan(wpa_s, &params);
+	if (!ret)
+		wpa_s->scan_res_handler = wpas_p2p_scan_res_join;
 
 	wpabuf_free(ies);