use IP addrs ; dont use own IP as server

using IP addrs for NTP avoids trouble from DNS being unavailable
and slightly reduces overall load
on NTP servers always use local clock as fallback

to avoid trouble when external servers are unreachable.
Uses predictable different fudge values
to allow servers to sync time from each other
when better time sources are absent.

hash function was tested with
[10,81,82,83].each do |x| puts (x-x/11)%9; end