Add configuration options for Default and vDNS default forwarders

The default forwarders are read from resolv.conf file
so basically it is just rendering a custom resolv.conf file
and configuring the location.
diff --git a/tests/pillar/cluster3.sls b/tests/pillar/cluster3.sls
index 0da7506..1f97957 100644
--- a/tests/pillar/cluster3.sls
+++ b/tests/pillar/cluster3.sls
@@ -68,6 +68,10 @@
     name: ntw-01
     bind:
       address: 127.0.0.1
+    dns:
+      forwarders:
+      - 8.8.8.8
+      - 8.8.4.4
     discovery:
       host: 127.0.0.1
     master: