Refactored and added more tests.Cleaned up netlink.

I've added more tests. We now have almost 55% coverage.
I've also reorganized netlink_linux codebase and moved
the non-RTNETLINK functions at the bottom. I've also
added some comments to some functions.

Docker-DCO-1.1-Signed-off-by: Milos Gajdos <milosgajdos83@gmail.com> (github: milosgajdos83)
Fixing Travis builds by allowing short tests.

Docker-DCO-1.1-Signed-off-by: Milos Gajdos milosgajdos83@gmail.com (github: milosgajdos83)