Sound Volume setting ignored after game return

[nblondiau]

The "Sound Volume" setting under "Configure / Sound" is only applied after attract initial start, or just after modifying the setting again.
Each time you're back to the frontend after a game return, the volume is back to 100 (even though the setting will still show the custom set value).

This should be easy to reproduce using a loud sound, and setting a very low volume to make the difference obvious.

Running Ubuntu 16.04.1, let me know if any additional info is needed.