fix: enable logprobs during spec decoding by default

[tjohnson31415]

As an optimization, vLLM disables logprobs when using spec decoding by default, but this would be unexpected to users of a hosted model that happens to have spec decoding. For our usage, we want logprobs enabled by default.

See: vllm-project#6485

Also moved setting of PORT env var to the adapter stage since it only works with the env var parsing in the adapter.

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[njhill]

Thanks @tjohnson31415!

[openshift-ci]

@tjohnson31415: The following test failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
ci/prow/smoke-test	5a71b15	link	true	/test smoke-test

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[openshift-ci]

New changes are detected. LGTM label has been removed.

[openshift-ci]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: dtrifiro, njhill, tjohnson31415

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[dtrifiro]

Forcing a merge as there's currently an OpenShift CI outage which prevents the smoke-test to run.