Reduce wait time for writing the EoR file

We were previously waiting a somewhat arbitrary five seconds before writing the EoR file in order to give all pipelines time to (potentially) "catch up" with the main pipeline. This was to make sure that the number of events given in the EoR (and EoLS) file corresponds to the actual number of events that were produced by SCDAQ.

In this MR I replace this five second wait with a check to make sure all pipelines have created raw files for the previous index (previous because the "current" index is the one that is currently being written, so is not included in the EoR/EoLS accounting).