Solve GID conflict between mediawiki and nasquenautes groups

Summary:
This is a follow-up for e056b0ca.

Fixes T1477.

Test Plan: no op for mediawiki, create group on Ysul for nasquenautes

Reviewers: dereckson

Reviewed By: dereckson

Maniphest Tasks: T1477

Differential Revision: https://devcentral.nasqueron.org/D1983