Correctly configure Salt minion for MySQL/MariaDB

References:

• UTSL: salt/config/__init__.py source code (default_include)
• https://docs.saltproject.io/en/3006/ref/configuration/minion.html

This is a follow-up for b44705d1.

Test Plan: On WindRiver, salt-call mysql.db_list as root

Reviewed By: Duranzed

Differential Revision: https://devcentral.nasqueron.org/D4060