[Samba] ActiveDirectory authorization broke from samba 2:4.7.6+dfsg~ubuntu-0ubuntu2.23 to 2:4.7.6+dfsg~ubuntu-0ubuntu2.27 (ubuntu 18.04)

[Daniel H. Peger]

For anyone stumbling across this issue. We were able to make the sssd/samba setup running again by
simply installing the debian winbind package and changing the access specification from 

    valid users = @"staff" 

to

    valid users = +"workgroup\staff"

The "workgroup" specification can be omitted if

    winbind use default domain = true

is configured in the global smb settings.

The mere presence of winbind seems to fix the setup.

Additionally we specified an id mapping. Not sure if this is actually needed though...

Thanks