test: Ensemble async callback execution (rework)

[yinggeh]

What does the PR do?

Occasionally only 10 traces are written to collected_traces.json at the check (expect 11). Give more time for the final trace to be collected.

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• test

Related PRs:

triton-inference-server/common#133
triton-inference-server/core#438
Previous PR: triton-inference-server/core#429

Test plan:

L0_trace
L0_simple_ensemble
L0_sequence_batcher
L0_backend_python

• CI Pipeline ID:
  29344284

Caveats:

Background

Related Issues: (use one of the action keywords Closes / Fixes / Resolves / Relates to)

• closes GitHub issue: Big performance drop when using ensemble model over separate calls #7650