Fix HLT prescaling when run on preloaded data
Fix HLT prescaling when run on preloaded data with HLTEventLoopMgr forcedSORTime
The seeding the random engine for the HLT prescaling is based on the event time (for reproducibility reasons). With this MR the event time is taken from the xAODEventInfo instead EventContext.eventID, which is commonly done.
This is due to the special case when the trigger is run in a partition with preloaded data and the parameter HLTEventLoopMgr.forceStartOfRunTime is set >0. In that case the EventContext.EventID is forced to the be the SOR time for each event. Using the EventContext.eventID would hence lead to a constant seed and a scewed prescaling.