Don't run "aphlict-listen" behavior if real-time notifications are disabled

Summary: Fixes T5277. We incorrectly ran this unconditionally.

Test Plan: Toggled setting on/off, verified behavior ran or did not run.

Reviewers: joshuaspence

Reviewed By: joshuaspence

Subscribers: epriestley

Maniphest Tasks: T5277

Differential Revision: https://secure.phabricator.com/D9418