ci: Fix L0_model_control_stress_vllm

[yinggeh]

What does the PR do?

• asyncio.get_event_loop() was deprecated in Python 3.12.
• Initialize gRPC client inside the async loop.

More details in the Jira ticket.

Checklist

• PR title reflects the change and is of format <commit_type>: <Title>
• Changes are described in the pull request.
• Related issues are referenced.
• Populated github labels field
• Added test plan and verified test passes.
• Verified that the PR passes existing CI.
• Verified copyright is correct on all changed files.
• Added succinct git squash message before merging ref.
• All template sections are filled out.
• Optional: Additional screenshots for behavior/output changes with before/after.

Commit Type:

Check the conventional commit type
box here and add the label to the github PR.

• ci

Related PRs:

Where should the reviewer start?

Test plan:

L0_model_control_stress_valgrind_massif_vllm--base
L0_model_control_stress_valgrind_vllm--base
L0_model_control_stress_vllm--base

• CI Pipeline ID:
  21756139

Caveats:

Background

Pipeline job failures

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

• closes GitHub issue: #xxx