code: public void maybeAddLatency(IAsyncCallback cb, InetAddress address, long latency)
      {
          if (cb.isLatencyForSnitch())
              addLatency(address, latency);
      }
docs: Track latency information for the dynamic snitch
  
  @param cb      the callback associated with this message -- this lets us know if it's a message type we're interested in
  @param address the host that replied to the message
  @param latency