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