[Bugfix] fix sleepmode level2 e2e test (#4019)

### What this PR does / why we need it?

enable sleepmode level2 e2e test and add the check logic to ensure the
nz is not enabled.

### Does this PR introduce _any_ user-facing change?

no

### How was this patch tested?

use e2e tests


- vLLM version: v0.11.0
- vLLM main:
83f478bb19

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

.github/workflows/_e2e_test.yaml

@@ -182,7 +182,7 @@ jobs:
           pytest -sv tests/e2e/multicard/test_torchair_graph_mode.py
           pytest -sv tests/e2e/multicard/test_data_parallel.py
           pytest -sv tests/e2e/multicard/test_expert_parallel.py
-          # pytest -sv tests/e2e/multicard/test_external_launcher.py
+          pytest -sv tests/e2e/multicard/test_external_launcher.py
           pytest -sv tests/e2e/multicard/test_single_request_aclgraph.py
           pytest -sv tests/e2e/multicard/test_fused_moe_allgather_ep.py
           pytest -sv tests/e2e/multicard/test_ilama_lora_tp2.py