Ticket #48969 - nsslapd-auditfaillog always has an explicit path
    
    Bug Description:
    In the current implementation, nsslapd-auditfaillog is not set,
    by default. Internally, the value is NULL, which let audit fail
    log share the same audit log file with nsslapd-auditlog.
    
    Once, some path is set to nsslapd-auditfaillog, it is not allowed
    to delete or set NULL or empty to it. That is, there is no way to
    go back to the default behaviour.
    
    There is another issue for the default value. Since search for
    nsslapd-auditfaillog under cn=config does not return anything,
    it is hard to find out where the failed logs are written.
    
    Fix Description:
    To solve the 2 issues, this patch changes the default value to an
    explicit path /path/to/logdir/audit.
    
    https://fedorahosted.org/389/ticket/48969
    
    Reviewed by wibrown@redhat.com (Thank you, William!)