rgw: int -> uint32_t transition for perm and perm_mask.

rgw: int -> uint32_t transition for perm and perm_mask.

This patch doesn't affect data structures. Changes were made
to the upper layers only. We rely there on the same assumption
like in case of req_state::perm_mask and RGWSubUser::perm_mask
that already are uint32_t. The assumption is presence of an
implicit conversion between int and uint32_t.

Signed-off-by: Radoslaw Zarzynski <rzarzynski@mirantis.com>