fix sleepmode level2 e2e test

Signed-off-by: wangx700 <wangxin700@huawei.com>

Author: wangx700

tests/e2e/multicard/test_external_launcher.py

@@ -154,6 +154,7 @@ def test_external_launcher_and_sleepmode():
     assert proc.returncode == 0
 
 
+@patch.dict(os.environ, {"VLLM_ASCEND_ENABLE_NZ": "0"})
 def test_external_launcher_and_sleepmode_level2():
     script = Path(
         __file__