Fix daemon auth issue

Summary: I touched this code recently but it needs an unusual special case because we call through with the "omnipotent user" from the daemons. As per the TODO below, this will all get cleaned up at some point.

Test Plan: Will make @poop verify.

Reviewers: btrahan, poop

Reviewed By: poop

CC: poop, aran

Differential Revision: https://secure.phabricator.com/D7356