Unmute and sanitize mixer levels on Jessie
In commit 2fc2715b, we drop alsa-utils -related bits. The corresponding
sanify_levels_on_card, which might be superseded by
PulseAudio on Jessie, or not. We should check that the mixer levels are
fine on various hardware (especially that is special-cased by alsa-utils
scripts) on startup.
Feature Branch: feature/jessie