Updating sa histories for open activities only. #3564

Only open PSC scheduled activities will have their states updated during operational import PSC sync

Previously we were running into the scenario where..

1. PSC activity canceled
2. Operational importer PSC data sync run
3. 'Canceled' activity state is changed to 'Scheduled'
Merge pull request #101 from NUBIC/3564-stop_canceled_event_scheduling

Prevent operational importer PSC sync from scheduling canceled activities.

Closes #3564.