Try harder to avoid LDAP access for RFC2307 mapping

Try harder to avoid LDAP access for RFC2307 mapping

        * fhandler_disk_file.cc (fhandler_base::fstat_by_nfs_ea): Rearrange
        to fall back to myself uid/gid in case we don't utilize Windows
        account DBs, just as prior to 1.7.34.
        * sec_helper.cc (cygpsid::get_id): Disable Samba user/group mapping per
        RFC2307 if we're not utilizing Windows account DBs.
        * security.cc (convert_samba_sd): Revert previous patch.

Signed-off-by: Corinna Vinschen <corinna@vinschen.de>