api.thread_churn test failing on Windows due to reattach problems

My new test api.thread_churn for #4334 is failing on Windows due to some re-attach issues:

+ .data is protected causing a crash on init
+ failing to take over threads: 80 such messages on the re-attach:
```

<...>
```

I tried to use logging to diagnose but hit another:
+ log file not being opened
Xref #2661 on ops appending: but here the option is not processed at all, leaving d_r_stats->loglevel 0.

It's not clear what's going on. The test makes 10 threads in the first burst. Is some state left over? Fixing logging would make it much easier to diagnose. For now I'm disabling the test on Windows.