cls_rbd, cls_rgw: use PRI*64 when printing/logging 64-bit values

caused segfaults in 32-bit build

Fixes: #3961
Signed-off-by: Dan Mick <dan.mick@inktank.com>
Reviewed-by: Sage Weil <sage@inktank.com>
(cherry picked from commit e253830abac76af03c63239302691f7fac1af381)