pybind/ceph_volume_client: add get, put, and delete object interfaces

pybind/ceph_volume_client: add get, put, and delete object interfaces

Wrap low-level rados APIs to allow ceph_volume_client to get, put, and
delete objects. The interfaces would allow OpenStack Manila's
cephfs driver to store config data in a shared storage to implement
highly available Manila deployments. Restrict  write(put) and
read(get) object sizes to 'osd_max_size' config setting.

Signed-off-by: Ramana Raja <rraja@redhat.com>
(cherry picked from commit d1bd171d6b6eb00c47168f38cec1a30f9c9f02bd)