R1:cf57f6385ba1

Fix some Calendar Event userPHID/hostPHID/"Creator" confusion in searching

Summary: Ref T11326. Align this stuff with "Host" and "hostPHID".

Test Plan: Searched for events by host.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T11326

Differential Revision: https://secure.phabricator.com/D16303