Fail explicitly instead of continuing with a warning if "phd.user" is misconfigured
Summary: Fixes T6806. We haven't seen users having issues with phd.user in a very long time.
Test Plan:
- Configured daemons to run as notepriestley, got a well-explained exception.
- Configured daemons to run as epriestley, got a clean start.
- Configured daemons with phd.user=null, got a clean start.
Reviewers: chad, areitz
Reviewed By: areitz
Subscribers: areitz
Maniphest Tasks: T6806
Differential Revision: https://secure.phabricator.com/D15726