Refresh MariaDB configuration

Summary:

• Use new FreeBSD /usr/local/etc/mysql/conf.d config directory
• Share same location for ZFS datadir
• Drop legacy MediaWiki and unsed OTRS config

Test Plan: Deploy on WindRiver

Reviewers: dereckson

Reviewed By: dereckson

Differential Revision: https://devcentral.nasqueron.org/D2655