Force a couple of Conduit results to the proper types in Calendar

Summary:
Ref T11706. Add some casts so we don't return "0" for false.

Also I forgot to document one of the things.

Test Plan: Called calendar.event.search.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T11706

Differential Revision: https://secure.phabricator.com/D16690