Calendar list objects that are ghost events should link to a ghost event, not the parent

Summary: Fixes T9034, Calendar list objects that are ghost events should link to a ghost event, not the parent.

Test Plan: Open All Events in Calendar, make sure ghost objects open the ghost instance, not the parent instance.

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley, #blessed_reviewers

Subscribers: epriestley, Korvin

Maniphest Tasks: T9034

Differential Revision: https://secure.phabricator.com/D13764