I literarly just figured out what this error is. So how Kerberos is divided up in alfresco is through two files, kerberos-authentication and kerberos-filter . The authentication file is responsible for CIFS/FTP/NFS while the filter is responsible for share/SSO. you're getting this error because in the filter file, the default is kerberos.authentication.sso.enabled=true if you don't need share(keep in mind just to turn it to true doesn't mean share SSO is done, there is more config that I haven't figured out), then turn it to false.
I hope that helps!
Thanks,
Michael