python/samba/provision: set unix session info for user session, used for sysvol acl reset
The unix session info is required and expected by e.g. many vfs modules. Missing unix session info leads to samba panic.
Typically in the python code auth_session_info_fill_unix() is used in combination with system-sessions. The sysvol acl code uses a user session for the Administrator user. auth_session_info_fill_unix() fails here to fill the unix token when winbind is not running.
So I add here a auth_session_info_set_unix() function to specify the unix token manually.