DiffusionCommitQuery - move phid to id mapping

Summary: Ref T5862. makes the exception work better

Test Plan: issued some queries from audit ui with and without repos - they worked

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: epriestley, Korvin

Maniphest Tasks: T5862

Differential Revision: https://secure.phabricator.com/D10268