fix: ollama still using tools with tool_choice="none" (#2047)

# What does this PR do?

In our OpenAI API verification tests, ollama was still calling tools
even when `tool_choice="none"` was passed in its chat completion
requests. Because ollama isn't respecting `tool_choice` properly, this
adjusts our provider implementation to remove the `tools` from the
request if `tool_choice="none"` is passed in so that it does not attempt
to call any of those tools.

## Test Plan

I tested this with a couple of Llama models, using both our OpenAI
completions integration tests and our verification test suites.

### OpenAI Completions / Chat Completions integration tests

These all passed before, and still do.

```
INFERENCE_MODEL="llama3.2:3b-instruct-fp16" \
  llama stack build --template ollama --image-type venv --run
```

```
LLAMA_STACK_CONFIG=http://localhost:8321 \
  python -m pytest -v \
  tests/integration/inference/test_openai_completion.py \
  --text-model "llama3.2:3b-instruct-fp16"
```

### OpenAI API Verification test suite

test_chat_*_tool_choice_none OpenAI API verification tests pass now,
when they failed before.

See

https://github.com/bbrowning/llama-stack-tests/blob/main/openai-api-verification/2025-04-27.md#ollama-llama-stack
for an example of these failures from a recent nightly CI run.

```
INFERENCE_MODEL="llama3.3:70b-instruct-q3_K_M" \
  llama stack build --template ollama --image-type venv --run
```

```
cat <<-EOF > tests/verifications/conf/ollama-llama-stack.yaml
base_url: http://localhost:8321/v1/openai/v1
api_key_var: OPENAI_API_KEY
models:
- llama3.3:70b-instruct-q3_K_M
model_display_names:
  llama3.3:70b-instruct-q3_K_M: Llama-3.3-70B-Instruct
test_exclusions:
  llama3.3:70b-instruct-q3_K_M:
  - test_chat_non_streaming_image
  - test_chat_streaming_image
  - test_chat_multi_turn_multiple_images
EOF
```

```
python -m pytest -s -v \
  'tests/verifications/openai_api/test_chat_completion.py' \
  --provider=ollama-llama-stack
```

Signed-off-by: Ben Browning <bbrownin@redhat.com>

llama_stack/providers/remote/inference/ollama/ollama.py

@@ -433,6 +433,12 @@ class OllamaInferenceAdapter(
         user: Optional[str] = None,
     ) -> Union[OpenAIChatCompletion, AsyncIterator[OpenAIChatCompletionChunk]]:
         model_obj = await self._get_model(model)
+
+        # ollama still makes tool calls even when tool_choice is "none"
+        # so we need to remove the tools in that case
+        if tool_choice == "none" and tools is not None:
+            tools = None
+
         params = {
             k: v
             for k, v in {