Deploy local-path-provisioner for persistent volumes in the admin cluster

Ref. swh/infra/sysadm-environment#5400 (closed)

I've only added the persistent local path provisioner as we already have the /srv/kubernetes/volumes mountpoint ready for it.

Compared to other clusters, this bumps the version to 0.0.28 which is the latest upstream, and drops the number of threads setting as it should not be needed in this cluster.