code: @SuppressWarnings("GoodTime") // should accept a java.time.Duration
    public void awaitHealthy(long timeout, TimeUnit unit) throws TimeoutException {
      state.awaitHealthy(timeout, unit);
    }
docs: Waits for the {@link ServiceManager} to become {@linkplain #isHealthy() healthy} for no more
  than the given time. The manager will become healthy after all the component services have
  reached the {@linkplain State#RUNNING running} state.
  
  @param timeout the maximum time to wait
  @param unit the time unit of the timeout argument
  @throws TimeoutException if not all of the services have finished starting within the deadline
  @throws IllegalStateException if the service manager reaches a state from which it cannot
  become {@linkplain #isHealthy() healthy}.