[Bugfix][Diffusion] Skip AllGather DLO weight restore on worker shutdown (#8103)

Signed-off-by: specture724 <specture724@gmail.com>
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>
Co-authored-by: Gao Han <hgaoaf@connect.ust.hk>

tests/diffusion/test_worker_wrapper_base.py

@@ -290,7 +290,7 @@ class TestWorkerWrapperBaseDelegation:
     def test_worker_shutdown_releases_model_before_cumem_pools(self, mocker: MockerFixture, native_kv):
         events: list[str] = []
         offload_backend = mocker.Mock()
-        offload_backend.disable.side_effect = lambda: events.append("offload")
+        offload_backend.shutdown.side_effect = lambda: events.append("offload")
         kv_manager = mocker.Mock()
         kv_manager.close.side_effect = lambda: events.append("kv")
         worker = DiffusionWorker.__new__(DiffusionWorker)
@@ -389,7 +389,7 @@ class TestWorkerWrapperBaseDelegation:
         mocker.patch("vllm_omni.diffusion.worker.diffusion_worker.shutdown_kv_connector")
         offload_backend = mocker.Mock()
         if cleanup_fails:
-            offload_backend.disable.side_effect = RuntimeError("offload cleanup failed")
+            offload_backend.shutdown.side_effect = RuntimeError("offload cleanup failed")
         worker = DiffusionWorker.__new__(DiffusionWorker)
         weights = torch.ones(1)
         weights_ref = weakref.ref(weights)