The CentOS6 ntp and ntpdate configuration can be used without changes on CentOS7.
The following configuration files are modified, but not tracked by rpm,
or not included in the packages:

/etc/ntp.conf

The files have been saved to /root/preupgrade/cleanconf.
Configuration files tracked by rpm are saved to the same directory by rule
"Store modified config files for packages with unchanged version".

Please note that the NTP package installed by default in CentOS7 is chrony.
To switch back to ntp, run "yum install ntp" and "yum remove chrony".