wlantest: Allow duplicate frame processing after decryption failure

wlantest: Allow duplicate frame processing after decryption failure

If a sniffer capture does not include FCS for each frame, but may
included frames with invalid FCS, it would be possible for wlantest to
try to decrypt the first received frame and fail (e.g., due to CCMP MIC
mismatch) because that particular frame was corrupted and then ignore
the following retry of that frame as a duplicate even if that retry has
different payload (e.g., if its reception did not show corruption).

Work around this by skipping duplicate frame detection immediately
following a decryption failure.

Signed-off-by: Jouni Malinen <jouni@codeaurora.org>