Make a more fine-grained test for Arthur's exit scanning for detecting DNSSEC issues
One relay operator we contacted because Arthur's exit test was failing 100% for them (see: legacy/trac#32864 (moved)) responded that the DNS resolution was actually fine as long as DNSSEC was not involved. Thus, we could enhance Arthur's test to have a more fine-grained check to give better advice/report backs to relay operators.