add server restart to prepare_servers()

system-test/maxtest/src/mariadb_nodes.cc

@@ -1452,7 +1452,7 @@ int Mariadb_nodes::prepare_server(int i)
             ssh_node(i, "mysql_install_db; sudo chown -R mysql:mysql /var/lib/mysql", true);
         }
     }
-
+    ssh_node(i, "service mysql restart", true);
     free(version);
     return ec;
 }