rbd: all object requests for images are asynchronous

Every object request used for image I/O is done asynchronously,
so there's no need to implement the wait in the object request
submit routine.

Signed-off-by: Alex Elder <elder@inktank.com>
rbd: memory debug

Add memory debug code.

Signed-off-by: Alex Elder <elder@inktank.com>
rbd: enable memory debug code

Mm-hmm.

Signed-off-by: Alex Elder <elder@inktank.com>