Ensure sudo can be installed on FreeBSD too

Summary:
The sudo unit worked only on Linux, as sudo
and the /usr/local/etc/sudoers.d directory
weren't provided.

This is a follow-up for f3a236a7.

Test Plan: Tested on router-001

Reviewers: dereckson

Reviewed By: dereckson

Differential Revision: https://devcentral.nasqueron.org/D2329