rados: implement read interface

Directly reads objects if possible, otherwise applies a regex to all
objects in the pool to find the ones being requested.

Signed-off-by: Noah Watkins <noahwatkins@gmail.com>
rados: fix error message

Signed-off-by: Noah Watkins <noahwatkins@gmail.com>
rados: implement delete interface

Signed-off-by: Noah Watkins <noahwatkins@gmail.com>