Unpublished Events show up for staff in side menus

[jefftriplett]

This is related to #1755, but I would classify this issue as a bug because there is no visual way to tell the difference between an unpublished event and a published event.

Please see this screenshot and notice that DjangoCon Africa has not been published from the admin yet. (Please note: They have already announced their dates and location, but they haven't blogged about it yet in case anyone is wondering.)

See the admin: