osd hitset tracking, librados command cleanup, librados wait_for_latest_map

and a few other odds and ends.

the punchline for this series is basic HitSet tracking in teh OSD and a
functional api test that touches a bunch of objects (reads), grabs teh hitsets,
and verifies that the touched objects are present.

A few other bits and pieces are mixed in here that are not strictly related,
but i'm not sure it is worth untangling the cleanups i did along the way from
the series unless they seem problematic.