Update kasp system test to work with .signed files

Update kasp system test to work with .signed files

We no longer accept copying DNSSEC records from the raw zone to
the secure zone, so update the kasp system test that relies on this
accordingly.

Also add more debugging and store the dnssec-verify results in a file.

(cherry picked from commit 57ea9e08c67bad6ddea446303772d8aec556208b)