Event RSVP Display should be fixed for Past vs. Present and Future events

Issue Description:
When an event is created especially Bonner Scholars event where a cohort of student can be added. They will show in the RSVP/Waitlist dropdown UI if the event is in the past. Instead the fix should be when an event is in the future or present the drop down should show RSVP/Waitlist but if the event is in the past it should show "absent from event"