Fix memory leak on EAPOL Authenticator error path

Fix memory leak on EAPOL Authenticator error path

wlan0: RADIUS No authentication server configured
MEMLEAK[0x999feb8]: len 1040
WPA_TRACE: memleak - START
[3]: ./hostapd(radius_msg_new+0x33) [0x8074f43]
     radius_msg_new() ../src/radius/radius.c:117
[4]: ./hostapd() [0x806095e]
     ieee802_1x_encapsulate_radius() ../src/ap/ieee802_1x.c:439
     ieee802_1x_aaa_send() ../src/ap/ieee802_1x.c:1496

For example, this error occured when I used WPS hostapd without
"eap_server=1" definition in configuration file.