When queueing search index tasks, include the "objectPHID" in the task metadata

Summary:
Ref T13151. See PHI719. One minor hiccup in debugging the issue (which ended up being "revision has 100K comments") was that the `SearchWorker` did not show which object it was indexing.

Add `'objectPHID'` to the queue call so you can see which object is affected from the web UI.

Test Plan:
  - Stopped daemons.
  - Used `bin/search index D123 --background` to queue a search task.
  - Viewed task details in web UI from `/daemon/`.
    - Before change: no indication of which object was being indexed.
    - After change: page helpfully shows that the task is indexing D123.

Reviewers: amckinley

Reviewed By: amckinley

Maniphest Tasks: T13151

Differential Revision: https://secure.phabricator.com/D19502

src/applications/search/worker/PhabricatorSearchWorker.php

@@ -15,6 +15,7 @@ final class PhabricatorSearchWorker extends PhabricatorWorker {
       ),
       array(
         'priority' => parent::PRIORITY_IMPORT,
+        'objectPHID' => $phid,
       ));
   }