Set domain level for DNS adapter

The DNS update needs that the zone exists on dns server.

We should be able to check against possible zone.

for example the label

www.ess01.arsinfo.it

can be stored as an A record either in zone
NSUPDATE
zone arsinfo.it
www.ess01 1.2.1.1 A

otrherwise you can say

NSUPDATE
zone ess01.arsinfo.it
www 1.2.1.1 A

The actual implementation uses the last. I'd like to set up a level to try if level=2 then you try zone arsinfo.it.