IBSS RSN: Do not start multiple Auth/Supp for same peer

IBSS RSN: Do not start multiple Auth/Supp for same peer

This avoids an issue when a received EAPOL-Key frame from a peer
is initiating IBSS RSN Authenticator and Supplicant for the peer
and the following new-STA-in-IBSS event from the driver is adding
yet another instance of Authenticator/Supplicant. The EAPOL-Key
RX case was already checking whether an instance had been started;
the driver new-STA event needs to do same.