Improve error handling for Aphlict.

Summary: Currently, any error thrown when instantiating an AphlictMaster will be assumed to be due to the master already existing. This is a bit overzealous because the documentation specifically states than an ArgumentError will be throw if "the LocalConnection instance is already connected".

Test Plan: Inspected the log message.

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley, #blessed_reviewers

Subscribers: epriestley, Korvin

Differential Revision: https://secure.phabricator.com/D9422