message: test: Fix intermittent failure in device index checking
  Lots of things can trigger device index weirdness, so don't
  compare device indexes to static values.
diff: @@ -257,7 +257,7 @@ fn test_repeated_address_additions() {
  }
  }
  ButtplugServerMessage::DeviceRemoved(dr) => {
  - assert_eq!(dr.device_index, 0);
  + assert_eq!(dr.device_index, device_index.unwrap());
  device_removed_called = true;
  }
  _ => {
  