For RouterOS 6.x a separate package 'ntp' exists. This adds server
functionality, but allows ip addresses for the client only. I added the
script 'rotate-ntp' to update addresses from names...
Now with RouterOS 7.x there's no extra package and the limitation does
no longer exist. So let's just drop the script.
This adds migration code, that...
* removes the script from configuration
* removes a scheduler from configuration
* sets the configured ntp pool name for ntp client
