Use FQDN as ptr name instead of octet

When multiple reverse zones are used and ptr records are generated from a records, the naming is not unique and causes errors.
I changed the PTR record handling a bit so that it uses FQDN instead of the last octet.
This solves errors like these when multiple reverse zones are used:

Error: Could not retrieve catalog from remote server: Error 400 on SERVER: Duplicate declaration: Dns::Record::Ptr[2] is already declared in file /etc/puppet/modules/dns/manifests/record/a.pp at line 25; cannot redeclare on node ...

I did not change the name of the resource definition, so i think it should not break existing configs.. Not tested though ! 

kr,
Stefan