Continue on bad daemon pid data

Summary: The rest of this code works if we hand off `array()`, and fataling here, while more correct, is harder for users to get out of (they have to go manually remove files) and not obvious.

Test Plan: Corrupted pid file and ran `phd stop`.

Reviewers: joshuaspence

Reviewed By: joshuaspence

Subscribers: epriestley

Differential Revision: https://secure.phabricator.com/D9749