Todo: Implement +cd on failure

[chani]

Most scripts will fail if there are DNSSEC issues, even those which might "show" DNSSEC issues - to properly test broken DNSSEC servers we should implement the cd-flag.

As discussed we're implementing a simple check (udp ipv4+ipv6 I'd say) in run.sh and if it doesn't work we'll retry with the cd-flag set. If that does work we do set a variable (CD) with content +cd. All dig- and delv-commands in the test scripts get ${CD} as param so that if run by run.sh all test-scripts will depending on the above check use +cd or not.

Doing the check in run.sh and only setting a variable will make sure that we do keep the test-scripts simple.