tests: Clear BSS table at the end of rsn_ie_proto_eap_sta

tests: Clear BSS table at the end of rsn_ie_proto_eap_sta

rsn_ie_proto_eap_sta followed by eap_ttls_mschapv2_session_resumption
showed a failure case where the special RSNE from rsn_ie_proto_eap_sta
ended up remaining in a wpa_supplicant BSS entry and the SELECT_NETWORK
command used the previous scan results without checking for changed AP
configuration. This resulted in test failure due to RSN IE being claimed
to be different in EAPOL-Key msg 3/4. This is not really a real world
issue, but try to avoid false failure reports by explicitly clearing the
BSS table at the end of rsn_ie_proto_eap_sta.

Signed-off-by: Jouni Malinen <jouni@qca.qualcomm.com>