- Replace setting the random seed with mocking out shuffle with reverse. This
makes tests easier to reason about while still being able to test correct
behaviour.
- Increases number of tracks to four to avoid test passing due to symetry in
plain and reversed lists.
- Made test_eot_track_with_random_after_append_playlist actually test eot and
not next.
- Found a test failure in handling of test_random_until_end_of_playlist, fix in
next commit.
