snd_worker/snd_disconnect_channel: don't call snd_channel_put if the channel has already been disconnected
snd_worker/snd_disconnect_channel: don't call snd_channel_put if the channel has already been disconnected

The snd channels has one reference as long as their socket is active.
The playback channel has an additional reference for each frame that is
currently filled by the sound device.
Once the channel is disconnected (the socket has been freed and the
first reference is released) snd_disconnect_channel shouldn't release
a reference again.

freedesktop-unofficial-mirror/spice__spice,fgouget/spice,alon/spice-server,elmarco/spice,freedesktop-unofficial-mirror/spice__spice,elmarco/spice,freedesktop-unofficial-mirror/spice__spice,fgouget/spice,Fantu/spice,SPICE/spice,fgouget/spice,freedesktop-unofficial-mirror/spice__spice,Fantu/spice,ya-mouse/spice,ya-mouse/spice,SPICE/spice,SPICE/spice,alon/spice-server,ya-mouse/spice,Fantu/spice,elmarco/spice,alon/spice-server,elmarco/spice,Fantu/spice,freedesktop-unofficial-mirror/spice__spice,fgouget/spice,alon/spice-server,alon/spice-server,elmarco/spice