gssint_get_mechanism_cred
mcred = gssint_get_mechanism_cred(ucred, &krb5_mechanism.mech_type);
mcred = gssint_get_mechanism_cred(ucred, &krb5_mechanism_old.mech_type);
mcred = gssint_get_mechanism_cred(ucred, &krb5_mechanism.mech_type);
mcred = gssint_get_mechanism_cred(ucred, &krb5_mechanism_old.mech_type);
sub_cred = gssint_get_mechanism_cred(candidate_cred, mech_type);
gss_cred_id_t gssint_get_mechanism_cred