Ghost NTP server on Debian 8.6

This is a server class machine with IPMI. The "ghost" NTP server that is causing the issue is running on the BMC processor on the system and not the main CPU.

As it has already been said, your IPMI BMC is (probably) the problem. If you cannot get to the web interface or ssh interface of the IPMI interface, you can try to get access using IPMI Tool on your Debian installation:

apt install ipmitool

Once installed, you can pass commands to the BMC like this (if it is on port 1):

ipmitool lan set 1 ipaddr 192.168.1.211

Here is a resource for IPMI network configuration with IPMITool. man ipmitool is always a good read if you get stuck...

You may reset the BMC if you need to.