Flake in test_timeout_does_not_expire

```
failures:
--
  |  
  | ---- tests::test_timeout_does_not_expire stdout ----
  | Error: Error { kind: Timeout, source: Some(reqwest::Error { kind: Request, url: "http://127.0.0.1:44713/echo?delay_ms=200", source: TimedOut }) }
  |  
  |  
  | failures:
  | tests::test_timeout_does_not_expire
  |  

```

https://pantheon.corp.google.com/cloud-build/builds;region=us-central1/0cc76168-d96c-45c7-9f64-891c371aba1f?project=rust-sdk-testing&e=13803378

Start with tests::test_timeout_does_not_expire and reproduce the reported failure using the test suite. Trace the timeout behavior around the request to /echo?delay_ms=200; done means the test no longer flakes or incorrectly reports a timeout under the intended conditions.

Written by the indexing model from the issue text.