Conpherence - fix unread counts

Summary: we weren't updating the "latest seen transaction PHID" properly. do that and ONLY do it from the view handler so we know the user got a real good chance of actually seeing the message. also we weren't searching through the transactions correctly; fix that.

Test Plan: sent a test user some messages. noted the proper count of unread messages.

Reviewers: epriestley, chad

Reviewed By: chad

CC: aran, Korvin

Maniphest Tasks: T2399

Differential Revision: https://secure.phabricator.com/D4677

src/applications/conpherence/controller/ConpherenceListController.php

@@ -41,11 +41,7 @@ final class ConpherenceListController extends
       }
       $this->setSelectedConpherencePHID($conpherence->getPHID());
 
-      $read_status =  ConpherenceParticipationStatus::UP_TO_DATE;
       $participant = $conpherence->getParticipant($user->getPHID());
-      $write_guard = AphrontWriteGuard::beginScopedUnguardedWrites();
-      $participant->markUpToDate();
-      unset($write_guard);
       $current_selection_epoch = $participant->getDateTouched();
     }