net/ntp: Replace the workaround from 98e34e8e2557 with a patch from upstream

43537eb9c3e5 circumvented an upstream patch which caused an IPv6
pool regresson. This patch removes the circumvention and replaces
it with an upstream patch planned for the new release of ntp.

Obtained from: src bc02e6558720

(cherry picked from commit 37ce58edb91a6fb06efa1c847ed8710f988d39c4)