Sound Manager master volume and mute don't work

[ezavada]

Volume sound is played at should be MasterVolume * soundVolume

Do this by making setVolume save the volume passed in but calculate the volume set at the OS level for each sound as multiplied by the master volume. Have the sound manager change the master volume then call snd.setVolume(snd.getVolume()) on each sound to change volume or mute.