rgw: read bucket metadata before writing it

In order to keep track of version.

Signed-off-by: Yehuda Sadeh <yehuda@inktank.com>
rgw: slightly simplify metadata abstraction

Signed-off-by: Yehuda Sadeh <yehuda@inktank.com>
rgw: tie bucket/user removal to mdlog differently

Signed-off-by: Yehuda Sadeh <yehuda@inktank.com>
rgw: json_encode json a bit differently

Encode map as a list, it's a more friendly representation.

Signed-off-by: Yehuda Sadeh <yehuda@inktank.com>
ceph_json: fix bool decoding

"false" means false.

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