[Bugfix] Fix modular kernel tests (#27707)

Signed-off-by: Bill Nell <bnell@redhat.com>

.buildkite/test-pipeline.yaml

@@ -498,6 +498,8 @@ steps:
   - tests/kernels/moe
   - vllm/model_executor/layers/fused_moe/
   - vllm/distributed/device_communicators/
+  - vllm/envs.py
+  - vllm/config
   commands:
     - pytest -v -s kernels/moe --shard-id=$$BUILDKITE_PARALLEL_JOB --num-shards=$$BUILDKITE_PARALLEL_JOB_COUNT
   parallelism: 2

tests/kernels/moe/modular_kernel_tools/common.py

@@ -138,6 +138,7 @@ class Config:
         }
 
         backend = self.all2all_backend()
+        vllm_config.parallel_config.all2all_backend = backend
         if backend is not None:
             env_dict.update({"VLLM_ALL2ALL_BACKEND": backend})