rbd: make pool_id a 64 bit value

If a format 2 image has a parent, its pool id will be specified
using a 64-bit value.  Change the pool id we save for an image to
match that.

Signed-off-by: Alex Elder <elder@inktank.com>
Reviewed-by: Josh Durgin <josh.durgin@inktank.com>
1 file changed