Stop writing PID files in daemons
Summary: Ref T13321. There are no more PID file readers, so we can stop writing them.
Test Plan: Ran bin/phd start, saw daemons doing stuff.
Reviewers: amckinley
Reviewed By: amckinley
Maniphest Tasks: T13321
Differential Revision: https://secure.phabricator.com/D20607