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/vrouter3.sls b/tests/pillar/vrouter3.sls
index d9ba886..807b510 100644
--- a/tests/pillar/vrouter3.sls
+++ b/tests/pillar/vrouter3.sls
@@ -18,6 +18,10 @@
       host: 127.0.0.1
     bind:
       address: 127.0.0.1
+    dns:
+      forwarders:
+      - 8.8.8.8
+      - 8.8.4.4
     interface:
       address: 127.0.0.1
       dev: eth0