rgw: copy actual stats from the source shards during reshard

rgw: copy actual stats from the source shards during reshard

Currently we don't copy the actual_stats field during reshard, which makes
resharded buckets show a size_utilized as 0, which further has the problem that
a subsequent object removal would subtract the object size from the 0 size
utilized showing up large uint64_t values. Copy the size_actual from the source
object in both cls and in reshard_process. This will fix the new buckets,
existing buckets will still have to go through a bucket check --fix for their
stats to be corrected.

Fixes: http://tracker.ceph.com/issues/36290
Signed-off-by: Abhishek Lekshmanan <abhishek@suse.com>
(cherry picked from commit beb90638ae3d5329653b61bae0d6714796c41d04)