fix: map IAM not-found errors to 404 in InfoCannedPolicy and RemoveUser

Merge the approved fix from pull request #8134.

rustfs/src/admin/handlers/policies.rs

@@ -320,7 +320,7 @@ impl Operation for InfoCannedPolicy {
                 error = ?e,
                 "admin policy state"
             );
-            S3Error::with_message(S3ErrorCode::InternalError, e.to_string())
+            iam_error_to_s3_error(e)
         })?;
 
         let body = serde_json::to_vec(&pd).map_err(|e| s3_error!(InternalError, "failed to serialize response: {:?}", e))?;

rustfs/src/admin/handlers/user.rs

@@ -510,9 +510,7 @@ impl Operation for RemoveUser {
             return Err(s3_error!(InternalError, "iam is not initialized"));
         };
 
-        let (is_temp, _) = iam_store.is_temp_user(ak).await.map_err(|e| {
-            S3Error::with_message(S3ErrorCode::InternalError, format!("failed to query temporary user state: {e}"))
-        })?;
+        let (is_temp, _) = iam_store.is_temp_user(ak).await.map_err(iam_error_to_s3_error)?;
 
         if is_temp {
             return Err(s3_error!(InvalidArgument, "cannot remove a temporary user"));