Race condition between measurements and rounds

[juliangruber]

There's a race condition between onMeasurementsAdded and onRoundStart event handlers, where a round can start before all measurements have been preprocessed. This currently leads to some measurements being ignored (see #232)

[bajtos]

Another effect of this race condition is that some measurements end up with no fraud assessment, see #64

[sentry-io]

Sentry Issue: SPARK-EVALUATE-47M