Start Trigger daemon alongside other daemons

Summary: Ref T6881. This won't do much of interest on third party installs yet, but it's stable and we don't need to hold it back any longer.

Test Plan: Ran phd start, saw the trigger daemon start up.

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T6881

Differential Revision: https://secure.phabricator.com/D11603