pep8 fixes
more pep8 fixes, removed duplicate SNI check for nsupdate.info

the super() call would do a duplicate check, so remove the nsupdate.info
check / SNI warning from base class.

in general, testing this based on .startswith("https://nsupdate.info") might
not work as we also have ipv4.nsupdate.info and ipv6.nsupdate.info.
Also, SNI might be used on other sites, too.