[Misc]: some minor issues in disaggregation test and benchmark tools

[Jeffwan]

Anything you want to discuss about vllm.

1. disaggregation benchmark replies on benchmark_serving.py which has the datasets dependency.
   

2. lsof command is not found
   

3. program exit immediately without waiting for two process. when I first run it, I though there's an issue.
   

4. logs need more polishment in kv_transfer tests. I can not easily check the run status.

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[Jeffwan]

/cc @KuntaiDu I cut a minor PR to address above issues.