Disable reload capability for Odderon

Summary:
Darkbot latest source code doesn't populate a pid file,
and this isn't really useful:

• to kill the process, systemd knows the pid as it's a non forking process
• we never used reload through systemd

Fixes T1233.

Test Plan: systemctl status odderon

Reviewers: dereckson

Reviewed By: dereckson

Maniphest Tasks: T1233

Differential Revision: https://devcentral.nasqueron.org/D1016