Rather than using servers["nsX"] syntax, utilize the nsX fixtures to
make the test code a bit more concise.
See fe5534291699572e67ad4a854b412e40c524307a
many of the zones in the dnssec system test were identical or
had only trivial differences, and it would be easier to keep track
of them if they were sourced from template files.
also, the extra_artifacts have been simplified and restored to
the test files.
the shell tests that queried servers to check correct signing
behavior (using dnssec-signzone, dnssec-policy and nsupdate),
as well as "rndc signing", private-type records, rndc zonestatus,
offline keys, etc, have been moved to tests_signing.py.
the minimal update test in the dnssec_update_test.pl script
was also moved here and the perl script has been removed.
begin converting DNSSEC validation tests from shell to python,
and simplify the name servers used in the test.
ns4, the name server used for validation tests, is now configured
using jinja2 templates.
ns8, which was previously used for testing unsupported, disabled
and revoked keys and trust anchors, has been removed. we now
use a jinja2 configuration in ns5 for this purpose.
the configurations in ns7 and ns6 didn't conflict with one another,
so the two servers have been merged into one.
