Set working directory for Odderon service

Summary:
Set working directory for the service

Reference: https://www.freedesktop.org/software/systemd/man/systemd.exec.html

Test Plan: Restart, ensure data files seems read

Reviewers: dereckson

Reviewed By: dereckson

Subscribers: Sandlayth

Differential Revision: https://devcentral.nasqueron.org/D890