main/openntpd: mv {init.d,conf.d}/ntpd -> openntpd

In preparation for ntpd init and conf script in
main/busybox-initscripts.

Handles migration of user edited /etc/conf.d/ntpd
and runlevel enablement.
main/busybox-initscripts: ntpd init and conf

Replaces openntpd init script and conf with the same
name.