Fix the error when starting the server

[snova-edwardm]

What does this PR do?

Pull the latest source code from GitHub and noticed two errors when starting the server.

• Missed import ResponseFormat in agent.py. Here is the error log

File "./llama_stack/llama-stack_main/llama_stack/apis/agents/agents.py", line 169, in AgentConfig
    response_format: Optional[ResponseFormat] = None
NameError: name 'ResponseFormat' is not defined. Did you mean: 'response_format'?

• Used incorrect parameters for subprocess in run,py. Here is the error log

  File "llamastack-sn-provider/lib/python3.10/subprocess.py", line 1722, in _execute_child
    args = list(args)
TypeError: 'Namespace' object is not iterable

Step to reproduce

1. Build the stack
   llama stack build --template sambanova --image-type conda --image-name llamastack-sn-provider

2. Star the server

SAMBANOVA_API_KEY="ABC" \
    llama stack run sambanova \
        --port 8008 \
        --image-name llamastack-sn-provider

Before submitting

• [N] This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).
• [Y] Ran pre-commit to handle lint / formatting issues.
• [Y] Read the contributor guideline,
  Pull Request section?
• [N] Updated relevant documentation.
• [N] Wrote necessary unit or integration tests.

[ashwinb]

@snova-edwardm thanks for the quick fixes but I just fixed both of these issues, sorry for the trouble

[ashwinb]

Closing...