Initialize status in krb5_ldap_parse_db_params

If db_args is non-null but empty, status could be returned without
being initialized; gcc with optimization correctly warns about this,
causing a build failure.  (This bug was introduced by
0b1dc2f93da4c860dd27f1ac997617b712dff383 which was pushed after the
1.11 release branch, so it isn't in any release.)