Exclude exhaust isMaster commands from latency metrics

In SERVER-47267 we exempted exhaust isMaster commands from slow query logging because they are expected to take ~10 seconds so would flood the logs with misleading slow query reports.

However it appears that they are still counted in our latency metrics (specifically the opLatencies section of serverStatus) which can be equally misleading. It would be good if we can exclude them from the latency metrics.