Canceling calendar events should deactivate the event

Summary: Closes T7943, Canceling calendar event should deactivate the event instead of destroying data.

Test Plan: Create an event, cancel it, see changed status icon, query for active events, event should not appear, query for deactivated events, event should appear in results.

Reviewers: #blessed_reviewers, epriestley

Reviewed By: #blessed_reviewers, epriestley

Subscribers: Korvin, epriestley

Maniphest Tasks: T7943

Differential Revision: https://secure.phabricator.com/D12604