media-keys: Do not suppress volume-change while playing
This effectively reverts commit 7d74327d ("media-keys: Skip volume-change feedback while playing"). The main problem is that we get into our own way when the volume-change happens multiple times in quick succession.
The feature is nice, but we need to improve it so that playback is only supressed when a proper audio stream is playing rather than just system sounds.
Resolves: #508 (closed)