[Samba] Windows Remote Assistance fails

[Ryan Bair]

I attempted to set up unsolicited remote assistance via group policy, but
connections to the client machines fail.

A network trace show the 'expert' machine doing a TGS-REQ to the DC which
responds with a KRB5KDC_ERR_POLICY. This seems to be the origin of the
problem.

I noticed in the request, the username of the 'novice' is given as the
Server Name but is otherwise pretty unremarkable.

Has anyone successfully gotten this working on a Samba4 AD domain?