Searching Calendar events by invitee should work now

Summary: Closes T8045, Searching Calendar events by invitee should work now

Test Plan: Open Advanced Search on Calendar, search by invitee, only events with invitee specified should be returned.

Reviewers: #blessed_reviewers, epriestley

Reviewed By: #blessed_reviewers, epriestley

Subscribers: Korvin, epriestley

Maniphest Tasks: T8045

Differential Revision: https://secure.phabricator.com/D12738