my.cnf template was broken for el7 mariadb

pid-file was missing in [mysqld_safe] causing startup failure:
  Process: 5140 ExecStartPost=/usr/libexec/mariadb-wait-ready $MAINPID (code=exited, status=1/FAILURE)
  Process: 5139 ExecStart=/usr/bin/mysqld_safe --basedir=/usr (code=exited, status=0/SUCCESS)
  Process: 5117 ExecStartPre=/usr/libexec/mariadb-prepare-db-dir %n (code=exited, status=0/SUCCESS)
 Main PID: 5139 (code=exited, status=0/SUCCESS)