fix:set use_beam_search false to aviod trace link broken

[RichardoMrMu]

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[RichardoMrMu]

FILL IN THE PR DESCRIPTION HERE

FIX #xxxx (link existing issues this PR will resolve)

BEFORE SUBMITTING, PLEASE READ https://docs.vllm.ai/en/latest/contributing/overview.html

related this issues [https://github.com//issues/14330]

If use beam search, self.engine_client.beam_search will not pass trace_headers to make trace link broken.

[RichardoMrMu]

@robertgshaw2-redhat hello, could u please review this pr and let me know if there is some wrong with this pr.