[Misc] Fix Current vLLM config is not set. warnings, assert to avoid issues in the future (#31747)

Signed-off-by: Lucas Wilkinson <lwilkins@redhat.com>
Signed-off-by: Lucas Wilkinson <LucasWilkinson@users.noreply.github.com>
Co-authored-by: Luka Govedič <ProExpertProg@users.noreply.github.com>

tests/plugins_tests/test_platform_plugins.py

@@ -31,7 +31,7 @@ def test_platform_plugins():
     )
 
 
-def test_oot_custom_op(monkeypatch: pytest.MonkeyPatch):
+def test_oot_custom_op(default_vllm_config, monkeypatch: pytest.MonkeyPatch):
     # simulate workload by running an example
     load_general_plugins()
     from vllm.model_executor.layers.rotary_embedding import RotaryEmbedding