fix `dns_prevent_single_point_failure` variable (#3728)

comparison that happens during `TASK [kubernetes-apps/ansible : Kubernetes Apps | Lay Down CoreDNS Template]` where the `dns-autoscaler` template is deployed causes coredns to fail deployment.  The error is caused by the variable `dns_prevent_single_point_failure` where an integer is being compared with a string. The resulting error:

```bash
'>' not supported between instances of 'int' and 'str'
```

prevents successful deployment of CoreDNS.  

The change makes the comparison happen between integers and allows CoreDNS to succeed.