test_dns: DNSSEC signing inserts empty text string components
update test_dns

Don't check NS records for now because they will only appear on zones.
If a hostname is a subdomain on a zone and not itself a zone, it will
lack NS records.

Also stop testing for ADSP, which we dropped in 126ea94ccf9d90d9b6b008bbba1c6d5ffa4460ec.
obviously put our stuff in /usr/local and not /usr