Updated the systemd service files to use environment files instead of environment variables as in previous versions of mariadb. Affected functionality was wsrep/galera.

To test, try:

1. setting wsrep_on to 1 and specifying an ip address (e.g. 127.0.0.1) in wsrep_cluster_address in /etc/my.cnf.d/galera.cnf
2. running galera_new_cluster
3. setting the first machine's ip in another machine's /etc/my.cnf.d/galera.cnf
4. running systemctl start mariadb on the second machine
5. mysql -e "show status like 'wsrep_cluster_size'" on both machines should result in 2