This warning comes from HttpComponents HttpClient. It occurs because the system you are communicating with has "negotiate" set. It's therefore trying first to find a Kerberos ticket, and failing that, falling back to NTLM.
There are two ways to fix this. First is to find out how to disable the warning in HttpClient. Second is to change the configuration of the target system's IIS from "Negotiate" to just plain "NTLM". I wish I knew how to do the former; I suspect there's a way to do if you just google the message.