The interaction between the mock network thread and the cloner thread is somewhat perilous. In this case, we wait for the cloner by waiting on its future. This assures the callback has been scheduled to the mock network thread, but it has not actually been run. This results in a tiny race if the next operation is a runUntil and the scheduler is a bit slow at scheduling the callback.

Solution is to call runReadyNetworkOperations after waiting for the cloner in that case.