fix: moonlight CI test mem regression (increase cache flush) (#1257)

Signed-off-by: Terry Kong <[email protected]>

Author: terrykong

examples/configs/recipes/llm/grpo-moonlight-16ba3b-4n8g-megatron.yaml

@@ -22,6 +22,7 @@ policy:
   optimizer: null
   megatron_cfg:
     enabled: true
+    empty_unused_memory_level: 1
     expert_model_parallel_size: 4
     pipeline_model_parallel_size: 4
     num_layers_in_first_pipeline_stage: 7