Fix ScheduleManager multiple enumeration
Fix ScheduleManager multiple enumeration

- Fix `ScheduleManager` multiple enumeration of the event times of a
scheduled event

AlexCatarino/Lean,JKarathiya/Lean,QuantConnect/Lean,JKarathiya/Lean,jameschch/Lean,jameschch/Lean,StefanoRaggi/Lean,jameschch/Lean,StefanoRaggi/Lean,AlexCatarino/Lean,StefanoRaggi/Lean,AlexCatarino/Lean,StefanoRaggi/Lean,StefanoRaggi/Lean,jameschch/Lean,jameschch/Lean,JKarathiya/Lean,QuantConnect/Lean,AlexCatarino/Lean,QuantConnect/Lean,QuantConnect/Lean,JKarathiya/Lean