move to sdk

[ivotron]

the rados-sdk branch has WIP on porting the cls to the RADOS sdk. Known things that the SDK does not provide yet (not an exhaustive list, as we're still investigating):

• the ENCODE, ENCODE_FINISH, ... macros. For example they’re used here https://github.com/uccross/skyhookdm-ceph-cls/blob/nautilus/src/cls/cls_tabular.h#L141 . Those are defined in a private include/encoding.h header.
• the other methods that the sdk doesn’t expose are the ones that work with lists of keys for the object map (cls_cxx_map_set_vals and cls_cxx_map_get_vals)

some alternatives to solving these:

• find different ways to accomplish the same without requiring more functionality exposed via the sdk header.
• expose it on our fork, and open a PR.
• open an issue on the upstream repo and wait for the community to address that.