ceph: support versioned reply

In versioned reply, inodestat, dirstat and lease are encoded with
version, compat_version and struct_len.

Based on a patch from Jos Collin <jcollin@redhat.com>.

Link: http://tracker.ceph.com/issues/26936


Signed-off-by: "Yan, Zheng" <zyan@redhat.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>