Fix Aphlict exit status
Summary: Fixes T6998. Based on https://groups.google.com/d/msg/nodejs/zF7GEoPccqw/n26c6gPaluwJ.
Test Plan: Ran Aphlict and forced an error. Saw error messages in the logs and also saw a non-zero exit status.
Reviewers: Blessed Reviewers, epriestley
Reviewed By: Blessed Reviewers, epriestley
Subscribers: Korvin, epriestley
Maniphest Tasks: T6998
Differential Revision: https://secure.phabricator.com/D11456