MFC rev 1.411:

• Remove NTP servers which do not resolve in DNS.
• Use pool.ntp.org servers where possible, thanks to Chuck Swiger <cswiger at mac dot com> .
• Update list of Swedish NTP servers, thanks to Fredrik Lindberg <fli+freebsd-current at shapeshifter dot se> .

PR: bin/75479
Approved by: re (scottl)