Fixes in DNS (experimental) EUCA-6575, EUCA-2770, EUCA-6546, EUCA-7072, EUCA-6242, EUCA-6463

- EUCA-6575, EUCA-2770: respond to 'instance-data'.
- EUCA-6546, EUCA-7072: use ns#.${system.dns.dnsdomain} when refering to nameserver and in NS records.
- EUCA-6242, EUCA-6463: handle service name DNS requests correctly.