scripts: add script to get worker latency

The worker latency must be low.

The node latency currently looks like this:

> quantile(r[,1] * 1000 * 1000, c(0.5, 0.90, 0.98, 0.99, 0.999))
      50%       90%       98%       99%     99.9%
  35.5320  100.4453 1768.3047 2583.9458 5864.9750

Signed-off-by: Sébastien Boisvert <boisvert@anl.gov>