fix(iam): keep error state on initial load failure (#2846)

Signed-off-by: houseme <housemecn@gmail.com>
Co-authored-by: houseme <housemecn@gmail.com>
Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>
Co-authored-by: loverustfs <hello@rustfs.com>
Co-authored-by: 安正超 <anzhengchao@gmail.com>

crates/iam/src/lib.rs

@@ -48,7 +48,7 @@ pub async fn init_iam_sys(ecstore: Arc<ECStore>) -> Result<()> {
 
     // 2. Create the cache manager.
     // The `new` method now performs a blocking initial load from disk.
-    let cache_manager = IamCache::new(storage_adapter).await;
+    let cache_manager = IamCache::new(storage_adapter).await?;
 
     // 3. Construct the system interface
     let iam_instance = Arc::new(IamSys::new(cache_manager));