rgw: make rgw_bucket_dir_entry backward compatible

Signed-off-by: Yehuda Sadeh <yehuda@inktank.com>
rgw: make rgw_cls_complete_op backward compatible

Signed-off-by: Yehuda Sadeh <yehuda@inktank.com>
rgw: renamed a few unit tests

Signed-off-by: Yehuda Sadeh <yehuda@inktank.com>
rgw: remove a few warnings

Signed-off-by: Yehuda Sadeh <yehuda@inktank.com>