by applying this patch we:
* no longer offer `ntpdate` to be set and started on boot;
* start offering the option to make `ntpd` set the date and time on boot itself.
the motivation for this change comes from the `ntpdate(8)` manpage:
> Note: The functionality of this program is now available in the ntpd(8)
> program. See the -q command line option in the ntpd(8) page. After a
> suitable period of mourning, the ntpdate utility is to be retired from
> this distribution.
offering `ntpd_sync_on_start` to be used will give folks the option to append `-g` into `ntpd`'s **command_args**.
according to `ntpd(8)`'s manpage:
> -g, --panicgate
> Allow the first adjustment to be Big. This option may appear an
> unlimited number of times.
>
> Normally, ntpd exits with a message to the system log if the
> offset exceeds the panic threshold, which is 1000 s by default.
> This option allows the time to be set to any value without
> restriction; however, this can happen only once. If the threshold
> is exceeded after that, ntpd will exit with a message to the
> system log. This option can be used with the -q and -x options.
> See the tinker configuration file directive for other options.