This configures the cipher suite to use for mcast traffic. The cipher suite to use for unicast traffic
is derived from this using the following algorithm:
Mcast cipher = WEP (64/128), Unicast cipher = TKIP
Mcast cipher = TKIP, Unicast cipher = TKIP
Mcast cipher = AES, Unicast cipher = AES.
This therefore determines the max unicast cipher suite the client can use to associate with
this interface.