Fix PR #2

Fix the mess that is #2, following some comments I made there

The autobuild files are big and complex enough that we make sure we don't add unnecessary
hard-to-follow code there.
Because it is already higher up in the file, and there is nothing that is needed to make autoproj auto-exclude it if the osdeps are setup right (which is what the pull request does).

In other words, it worked so far because if freenect is disabled autoproj auto-excludes the orogen package as well.