pack-bitmap: uninteresting oid can be outside bitmapped packfile

bitmap_has_oid_in_uninteresting() only used bitmap_position_packfile(), not bitmap_position(). So it wouldn't find objects which weren't in the bitmapped packfile (i.e., ones where we extended the bitmap to handle loose objects, or objects in other packs). As we could reuse a delta against such an object it is suboptimal not to use bitmap_position(), so let's use it instead of bitmap_position_packfile(). Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Christian Couder <chriscool@tuxfamily.org> Signed-off-by: Junio C Hamano <gitster@pobox.com>