message: Reduce the number of threads iron uses during tests
  It defaults to 8 * num_cpus, and we leak these threads since we can't
  shut iron down, so on my 20-core machine it was hitting 11,500 idle
  threads during the test run.
diff: @@ -430,7 +430,11 @@ impl Server {
  context: &dyn Context,
  ) -> Result<Self, Error> {
  let cratesfyi = CratesfyiHandler::new(template_data, context)?;
  - let inner = Iron::new(cratesfyi)
  + let mut iron = Iron::new(cratesfyi);
  + if cfg!(test) {
  + iron.threads = 1;
  + }
  + let inner = iron
  .http(addr)
  .unwrap_or_else(|_| panic!("Failed to bind to socket on {}", addr));
  