net/ntp: ntpd does not connect to NTP server with link local IPv6 address

Upstream bug 3943 (https://bugs.ntp.org/show_bug.cgi?id=3943) discusses:

Starting with 4.2.8p18 ntp does not synchronize or even connect to the
configured NTP server any more. ntp stays in .INIT. state indefinitely
and checking the network traffic shows that ntp does not attempt to
contact the NTP server.

This is regression introduced by the fix for upstream bug 3913. This
is a similar bug I reported upstream (ntp bug 3841).

Obtained from: src 381956e26756

(cherry picked from commit 453bd9639bae31c05fa0eda782af0926a12a8b42)