ntp: T3904: Fix NTP pool associations

As of NTP 4.2.7, 'nopeer' also blocks pool associations.

See https://bugs.ntp.org/show_bug.cgi?id=2657

See also https://github.com/geerlingguy/ansible-role-ntp/pull/84

(cherry picked from commit 854c68d43d8f1cf20417edd12284ea20f9e7ec9a)