SW: Clean up boss music code. Remove unnecessary calls and checks
Compare changes
This partially addresses #37 in that the boss music now stops playing properly at all times.
Several parts of the boss music code were also unnecessary. It still resumes playback fine on save load.
It will probably still need a rework later to properly support multiple bosses active at the same time.
Regarding #37 I haven't figured out yet what causes the boss music to not play sometimes, however, I haven't been able to reproduce it after making these changes.