tests: Make offchannel_tx_roc_gas more robust

It was possible for this test case to fail if cfg80211 BSS cache
included an entry for the same BSSID on another channel from an earlier
test case. Fix this by epxlicitly flushing the cache. In addition, use
scan_for_bss() to make the test less likely to fail in case of heavy CPU
load.

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

tests/hwsim/test_offchannel_tx.py

@@ -22,7 +22,8 @@ def test_offchannel_tx_roc_gas(dev, apdev):
 
     wpas = WpaSupplicant(global_iface='/tmp/wpas-wlan5')
     wpas.interface_add("wlan5", drv_params="no_offchannel_tx=1")
-    wpas.scan(freq="2412")
+    wpas.flush_scan_cache()
+    wpas.scan_for_bss(bssid, freq=2412)
     anqp_get(wpas, bssid, 263)
     ev = wpas.wait_event(["GAS-QUERY-DONE"], timeout=10)
     if ev is None: