Reject Group Key message 1/2 prior to completion of 4-way handshake

Reject Group Key message 1/2 prior to completion of 4-way handshake

Previously, it would have been possible to complete RSN connection by
skipping the msg 3/4 and 4/4 completely. This would have resulted in
pairwise key not being configured. This is obviously not supposed to
happen in practice and could result in unexpected behavior, so reject
group key message before the initial 4-way handshake has been completed.

Signed-off-by: Jouni Malinen <j@w1.fi>