Try nodejs before node when starting notification server

Summary: Fixes T5278. This isn't completely perfect (if you have the other node binary, it will fail to detect that it's wrong) but we can maybe wait for that to happen and devise some kind of "is this binary really node?" test if users actually hit it.

Test Plan: Faked things, hit the error; unfaked them and hit the normal flow.

Reviewers: joshuaspence

Reviewed By: joshuaspence

Subscribers: epriestley

Maniphest Tasks: T5278

Differential Revision: https://secure.phabricator.com/D9419