set nameservers to default empty value in network config v2 parser

Change-Id: I931841bc3b6be4f4a09e9a5b470bdfc0cc32f8c7

Author: FlorianLaunay

cloudbaseinit/metadata/services/nocloudservice.py

@@ -332,7 +332,7 @@ def _parse_addresses(self, item, link_name):
                 gateway=gateway)
             routes.append(route)
 
-        nameservers = item.get("nameservers")
+        nameservers = item.get("nameservers", {})
         nameserver_addresses = nameservers.get("addresses", []) \
             if nameservers else []
         searches = nameservers.get("search", [])