allow meta.nfs_server.allow_from_entries to be overridden by other spiff templates

For deployments using hostnames instead of static IPs, this allows the list to change scoped by hostnames:

```yaml
meta:
  nfs_server:
    address: (( "0.data.cf1." meta.deployment_name ".microbosh" ))
    allow_from_entries:
      - (( "*.*.cf1." meta.deployment_name ".microbosh" ))
```