FLAKE: "unknown file SEH exception with code 0xc0000005 thrown in TearDown()" failure on Windows

https://source.cloud.google.com/results/invocations/804a4860-c905-46c2-8797-4ce1d4156699/targets/%2F%2Ftest%2Fcore%2Ftransport%2Fchttp2:settings_timeout_test/tests

Yet another instance of the Windows "SEH exception" failure:

```
unknown file
SEH exception with code 0xc0000005 thrown in the test body.
```