fix the error of TTFT and TPOT while the bench target is chatqna_qlist_pubmed

[leslieluyu]

Description

missing streaming config of chatqna_qlist_pubmed
Lack of the config will cause the error of "next token latency"

example

End to End latency(ms),    P50: 25875.62,   P90: 34988.45,   P99: 56357.57,   Avg: 26382.29
Time to First Token-TTFT(ms),   P50: 25875.21,   P90: 34987.96,   P99: 56357.17,   Avg: 26381.87
Time Per Output Token-TPOT(ms),   P50: 0.00,   P90: 0.00,   P99: 0.01,   Avg: 0.00

Issues

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Type of change

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• Bug fix (non-breaking change which fixes an issue)

Dependencies

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Tests

Describe the tests that you ran to verify your changes.

1. deploy the chatqna v1.2
2. git pull the evel code
   3.use locust command line to verify bench-target "chatqna_qlist_pubmed"

locust --locustfile ~/GenAIEval/evals/benchmark/stresscli/locust/aistress.py --host http://IP:PORT --run-time 60m  --max-output 128  --seed 1024 --processes 8 --users 128 --spawn-rate 100 --max-request 640 --bench-target chatqna_qlist_pubmed --llm-model meta-llama/Meta-Llama-3-8B-Instruct --stop-timeout 120 --csv /opt/opea/test_reports/test_locust/ --headless --only-summary --loglevel WARNING --json