fix: check event loop state before stopping in NetworkThread.close() #34334

Fixes #34248

Add is_running() check in NetworkThread.close() to prevent timeout when event loop is already stopped on NetBSD.

<!--e57a25ab6845829454e8d69fc972939a-->

The following sections might be updated with supplementary metadata relevant to reviewers and maintainers.

<!--006a51241073e994b41acfe9ec718e94-->

Code Coverage & Benchmarks

For details see: https://corecheck.dev/bitcoin/bitcoin/pulls/34334.

<!--021abf342d371248e50ceaed478a90ca-->

Reviews

See the guideline for information on the review process. A summary of reviews will appear here.

<!--174a7506f384e20aa4161008e828411d-->

Conflicts

Reviewers, this pull request conflicts with the following ones:

• #34346 (test: use IP_PORTRANGE_HIGH on FreeBSD for dynamic port allocation by w0xlt)

If you consider this pull request important, please also help to review the conflicting pull requests. Ideally, start with the one that should be merged first.

<!--5faf32d7da4f0f540f40219e4f7537a3-->

why would it already be closed, and why would the check help anything to improve the situation?

I think the problem is not that it is already stopped but that it does not stop within 10 seconds:

AssertionError: Predicate ''''
        wait_until_helper_internal(lambda: not self.network_event_loop.is_running(), timeout=timeout)
''' not true after 10.0 seconds

=> is_running() keeps returning True after 10 seconds.

Closing for now. I'd guess this is an LLM-generated one-shot pr that was submitted blindly and the contributor went away?