Fix nonstatic_routes tests

These two tests seems to fail.

ipv4_ignore_nonstatic_routes ipv6_ignore_nonstatic_routes

First of all, I see no cleanup, and routes remains there a few of the following tests. Second, ip command takes too much time even on my machine to complete (I was willing to wait around 10m and only 400000 routes were processed, so to 2M it is five time more, 50 minutes just adding the routes, and then delete them is nonsense). I do not know if NM is slowing it down, but I guess the bottleneck here is either ip or kernel. What worked for me as a cleanup was deleting veth pair (eth3), so I would suggest converting it to veth interface using * Prepare simulated device... and @terdown_testveth tag should take care of it (as it deletes the device, so routes will go as well).

This statred to show up now, since the tests had even version (1.36), which is bad, because before 1.36 is released, we have to use 1.35 (odd version), which is current main branch. Now, nm-1-36 branch has forked and main is 1.37 and the test started to fail. Basically, if it is new feature that is not going to be backported to even branches, always use version of the current main (which is odd).

Assinging @djasa as the author of the tests. Thanks!