samba-server.yml: Improve include_wrappers a tiny bit

Make samba-options-local.ycp compile in the context of "nearest"
self-contained include, not in a "toplevel" client. This will make the
compilation a tiny bit faster.
Merge pull request #430 from yast/samba-server-improve-include-wrappers

samba-server.yml: Improve include_wrappers a tiny bit