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