Disable galera clustering in openstack to use single instance mysql db

I have a galera cluster setup for openstack which is not working properly.

So instead of the cluster, i have now decided to use a single instance mysql(mariaDB) that is run in a lxc container as database.

But i don't know hoew can i disable the clustering. I found an option

 wsrep_on = OFF

would do this.

But in which configuration file i should specify this? Should be it in my.cnf ?

I googled for the solution but found nothing. Could someone help me to find a solution or reference?