It is possible for a scan to fail to see Probe Response or Beacon frame
under heavy load (e.g., during a parallel-vm.sh test run) since the
dwell time on a chanenl is quite short. Make the test cases using
INTERWORKING_SELECT more robust by trying again if the first attempt
does not find a matching BSS.
Signed-off-by: Jouni Malinen <j@w1.fi>