It was possible for the first wt.clear_bss_counters(bssid) call to fail
the test if timing worked out in a way that the wlantest process had not
received any Beacon frames from the first AP. Run a directed scan for
both of the BSSs before starting the test validation steps to make sure
such a case cannot fail this test case.
Signed-off-by: Jouni Malinen <j@w1.fi>