decom IAM, Bucket metadata properly (#15220)

Current code incorrectly passed the
config asset object name while decommissioning,
make sure that we pass the right object name
to be hashed on the newer set of pools.

This PR fixes situations after a successful
decommission, the users and policies might go
missing due to wrong hashed set.

docs/distributed/rw.json

@@ -0,0 +1,14 @@
+{
+  "Version": "2012-10-17",
+  "Statement": [
+   {
+    "Effect": "Allow",
+    "Action": [
+     "s3:*"
+    ],
+    "Resource": [
+     "arn:aws:s3:::*"
+    ]
+   }
+  ]
+ }