Fix Odderon systemd unit type

Summary:
Until recently, systemd ignored case for parameters,
but now, parameters are case sensitive.

As such, Odderon service doesn't start, with the following error:
Failed to parse service type, ignoring: Simple

Ref. T1233

This is a follow-up for f7788aa6.

Test Plan: systemctl status odderon

Reviewers: Sandlayth, dereckson

Reviewed By: dereckson

Maniphest Tasks: T1233

Differential Revision: https://devcentral.nasqueron.org/D1014