Really fix #6 and cleanup conditoinal expressions.

I closed #6 too early, I still got errors. This now fixes #6 for me. Major change is to test for static interface first and then skip everything else (even checking for network manager).

Please test if the non-static cases still work as you expect. I'm unable to test with my current setup.

Beside this I simplifies conditional expressions so they are more readable. You may want to look at the commit-messages and into the details to see some ticks I just learned.