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