Decrypt MPPE keys and derive PMK from RADIUS exchange if RADIUS
shared secret is known. Use the derived PMK when trying to derive
PTK during 4-Way Handshake.
Allow pre-configuration of passphrases (-p<passphrase>) to provide
enough information for wlantest to be able to derive PMK for each
BSS and PTK for each STA going through 4-Way Handshake (at least
message 2 and 3 needs to be received).