pykickstart: Run test cases in order of name.

This should ensure the test casnes are always running in the same order,
regardless of the target machine. We're just using the class name here, which
should be sufficient enough to address the issue.

Now the following build should be fixed:

http://hydra.nixos.org/build/5425811

Big thanks to @rbvermaa for being a *really* great help debugging the problem
quickly, because I couldn't reproduce it here (the run order of the test cases
on my machine were 'accidentally' right).

Signed-off-by: aszlig <aszlig@redmoonstudios.org>