fix conpherence menu selection

Summary: i think the DOM changed in conpherence with the menu upgrades. just noticed that when you select a new conpherence the old one is not de-selected. this fixes it by updating the javascript to ascend one node higher and then use DOM.scry with the right data sigil to get the nodes

Test Plan: read some messages, noted only the one I was reading had the entry highlighted in the left.

Reviewers: epriestley

Reviewed By: epriestley

CC: aran, Korvin

Maniphest Tasks: T2399

Differential Revision: https://secure.phabricator.com/D4819