Code review comment for lp:~rsalveti/indicator-sound/adding-support-for-sound-per-roles

What's happening isn't that we're getting a value for every little change, we're getting periodic updates, but QML blocks on the call. So we end up creating a "jumpy" slider if we take too long to respond to it. This was happening with the AS support earlier. So it needs to be async not because we're getting every little change but more because we need to respond to the message as fast as possible to avoid the UI from blocking. (which it shouldn't, but apparently that's a difficult problem to tackle on the QML side)