Don't show comment draft state to non-object-owners
Summary: Fixes T7720. We currently leak the "draft" state of checkboxes; never treat checkboxes as drafts if you can't mark them.
Test Plan: Checked a box, reloaded page in other browser. Previously, the draft state partially propagated. Now, it no longer does.
Reviewers: btrahan, chad
Reviewed By: chad
Maniphest Tasks: T7720
Differential Revision: https://secure.phabricator.com/D12262