Fix Conphernce sometimes searching wrong room

Summary: I passed this in as a config, but need to parse it live when threads change, otherwise the wrong room could be searched.

Test Plan: Search in one room, click a second, search again, see correct results.

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: Korvin

Differential Revision: https://secure.phabricator.com/D16707