[rollout] fix: resource pool name in standalone mode

[PeterSH6]

What does this PR do?

fix resource pool name in standalone mode

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[PeterSH6]

TODO: CIs should be added to the standalone reward model (genRM)

[yyDing1]

relevant ci has been added in https://github.com/volcengine/verl/blob/main/.github/workflows/reward_model_vllm.yml and https://github.com/volcengine/verl/blob/main/.github/workflows/reward_model_sglang.yml