minor change for buffalo test of client-oss,

let lconf be able to accept --mds_sec but ignore it.
llmount.c is able to accept mds_sec option but ignore it,
so it doesn't need change for this purpose.

for h_hd_sec_client_oss, it also needs the change to lconf
to accept --sec but ignore it.

after client-oss landing, we will make it integrated.