Fix Conpherence NUX showing empty Joinable Rooms

Summary: I moved this to setContent with the new search result layout, but failed to update NUX here.

Test Plan: Leave all rooms, get Joinable Rooms with list of 10 rooms.

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: Korvin

Differential Revision: https://secure.phabricator.com/D16743