change the host path storage to use ibm cloud nfs or block storage service

[animeshsingh]

provide example using nfs or block storage - else remove the word scalable from this

[Tomcli]

I think this example was created 3 years ago and back then there was no good solution for scalable databases on Kubernetes. But in today's standard, probably is worth to take a look at https://github.com/presslabs/mysql-operator to deploy a MySQL cluster for a truly scalable environment.