rados: add OsdCommand & OsdCommandWithInputBuffer functions
rados: add OsdCommand & OsdCommandWithInputBuffer functions

These functions wrap rados_osd_command and allow the user to send
"command JSON" to OSDs.

Signed-off-by: John Mulligan <eda8ad33169deab44f9fe65847f99e368da6c91b@redhat.com>

ceph/go-ceph,ceph/go-ceph,ceph/go-ceph