The included smb.conf looks pretty outdated. It includeds many parameters that are no longer even supported by samba, for example; " domain controller = foo.com " is no longer supported.
It's the default smb.conf that ships with samba; are you sure you don't have a previous samba install that you're looking at the configuration for? (By default, the current smb.conf is *not* replaced on an upgrade...)
I am positive that it is the default smb.conf included with the samba package in 5.8.1. The computer 5.8.1 was installed on was formatted during install, so it can be no other.
'domain controller' is deprecated, but still accepted according to the man page. In any case, it's straight out of the samba tarball, so it should be as up to date as any sample configuration.
If you use it, and then view your log files you will notice errors. 'unknown parameter encountered: "domain controller" ' I belive it should be removed to avoid confusion.
domain controler is disabled in the config files in the beta release