Do not enable bgscan when driver takes care of BSS selection

There is no need to request periodic bgscans when the driver claims
to have capability for roaming within ESS. Ignoring the bgscan
configuration allows the same configuration file to be used both
with drivers the handle roaming and with drivers that don't.

wpa_supplicant/wpa_supplicant.c

@@ -527,6 +527,8 @@ const char * wpa_supplicant_state_txt(enum wpa_states state)
 
 static void wpa_supplicant_start_bgscan(struct wpa_supplicant *wpa_s)
 {
+	if (wpas_driver_bss_selection(wpa_s))
+		return;
 	if (wpa_s->current_ssid == wpa_s->bgscan_ssid)
 		return;