Don't just store the id in the metadata but a JSON object with
the node name. This makes it possible to easily introspect the
metadata and also extend the metadata with more fields later.
Instead of matching the metadata id to the global ids we now
have to match it against the name.
Check if the properties got update before we try to parse them.
If they are not updated, they might be empty and we would lose
our previously parse values.
Fixes default volume in alsa-mixer.
