DNS module: Update list of test domains to resolve

This will suppress resolving "big brothers" sites which can lead to privacy leak or stress of our users.

By resolving turris.com, we get advantage of DNSSEC-enabled domain in com TLD, by debian.org and fsf.org, in org TLD. Also duckduckgo.com and wikipedia.org should be large enough sites that can provide sufficient uptime and reliability.

Also mark DNS attempts with their meaning and desired results.