[Pkg-samba-maint] Bug#678834: guest users create locally inaccessible files owned by nobody

[email.bug at arcor.de]

Package: samba

Collaboration with guests is broken, and a truel solution is needed. 

Sleeping over it, the idea I proposed in #678616 (a different "guest account" definition)
really isn't solving the problem in general. Its way too static, to be right for everybody.

For net usershares at least, samba has the information who created the share,
thus it could use that when samba guests are creating files.

Ideally, the file could still be identifiable to the samba guest with
its group ownership set to samba-guest.