Cleaner templating

This style of templating has the same effect as before, but its a bit
easier to read.
I had the nameservers explicitly not an Array, because of the way how hiera works. I.e. 
I have hiera hierarchy:
networkservers/dnssrv1.yaml
networkservers/dnssrc2.yaml

then, when in networkservers/dnssrv1.yaml is an array:
```yaml
dhcpd::nameservers:
  - 1.1.1.1
  - 2.2.2.2
```
and in networkservers/dnssrv2.yaml is an other array:
dhcpd::nameservers:
  - 2.2.2.2
  - 1.1.1.1

then when I retrieve the array via hiera, the order is always the same, regardless in which order its specified in 
hiera. Reason for this is, when I want to netboot/autoinstall one DNS server, it should get correct DNS infos etc. from the other, and vice-versa.

Could you make it conditional? I.e. if nameservers.is_array ... else ...

The rest looks all fine to me.

thanks,
Sebastian