Do not insert ENT when delegate above delegate

consider these records:
a.b.c.delegate.test.dyndns 600 NS ns1.test.dyndns
c.delegate.test.dyndns 600 NS ns1.test.dyndns

When deleting c.delegate.test.dynds we would search for records below
and find a.b.c.delegate.test.dyndns. This would cause a ENT to be inserted.

So, if we delete something at a high level, we make sure we ignore NS records that are below it when searching to see
if we need to insert ENT's.
Add regression test for previous commit
Merge branch 'rfc2136/hacking' of https://github.com/mind04/pdns into rfc2136-hacking
Correct odername/auth when increasing serial
Fix narrow test result
Correct inserting of ENT records
Merge branch 'rfc2136-hacking' of github.com:cyclops1982/pdns into rfc2136-hacking