Distribution packaged ntpd has servers preconfigured in ntp.conf so
there's no point in trying to add them again during FreeIPA server
installation.
Also fix the code to always put fudge line right after the local server
line as required by ntpd.
https://fedorahosted.org/freeipa/ticket/6486
Reviewed-By: Petr Spacek <pspacek@redhat.com>