Description of problem:
radosgw-admin user stats showing 0 value for "size_utilized" and "size_kb_utilized" fields :

# radosgw-admin user stats --uid=gsitlani
{
    "stats": {
        "size": 13143938329,
        "size_actual": 13145272320,
        "size_utilized": 0,
        "size_kb": 12835878,
        "size_kb_actual": 12837180,
        "size_kb_utilized": 0,
        "num_objects": 1001
    },
    "last_stats_sync": "0.000000",
    "last_stats_update": "2021-07-23T19:56:18.114977Z"
}

Version-Release number of selected component (if applicable):
16.2.0-107.el8cp

How reproducible:
1. Deploy a 5.x cluster
2. Create a bucket or two in the cluster. 
3. Write some objects to the bucket and check the radosgw-admin bucket stats and radosgw-admin user stats outputs 

Actual results:
radosgw-admin user stats showing 0 value for "size_utilized" and "size_kb_utilized" fields.

Expected results:
Correct value for "size_utilized" and "size_kb_utilized" fields should be displayed in the user stats

Additional info :
https://bugzilla.redhat.com/show_bug.cgi?id=1984261#c13