Unschedule scheduled event status update only if last update was successful (#168)

This PR fixes an issue that prevented scheduled event status updates
from running again if they failed. This happened because, before each
update, the events would be synchronized. The `ScheduleOnStatusUpdated`
field would be set even if it's already `true`, which will cause it to
be set to `false` for unsuccessful updates. The issue is fixed by
surrounding the field set call with a condition that will prevent
setting the field from `true` to `false`

src/Services/Update/ScheduledEventUpdateService.cs

@@ -114,7 +114,11 @@ public sealed class ScheduledEventUpdateService : BackgroundService
             var eventData = data.ScheduledEvents[@event.ID.Value];
             eventData.Name = @event.Name;
             eventData.ScheduledStartTime = @event.ScheduledStartTime;
-            eventData.ScheduleOnStatusUpdated = eventData.Status != @event.Status;
+            if (!eventData.ScheduleOnStatusUpdated)
+            {
+                eventData.ScheduleOnStatusUpdated = eventData.Status != @event.Status;
+            }
+
             eventData.Status = @event.Status;
         }
     }