sound: don't store client in SndChannel
sound: don't store client in SndChannel

The base RedChannel already keeps a list of channel clients, so there's
no need for the SndChannel to also keep track of the client itself.

Since the SndChannel only supports a single client (whereas other
channels may have some partial support for multiple clients), I've
provided a convenience function for getting the client and warning if
there is more than one.

Signed-off-by: Jonathon Jongsma <c7254805a17bd5c41e24c3a278fcbf3afcdfb0fa@redhat.com>
Acked-by: Christophe Fergeau <05b95054a663c388a4e33d95828cb30f0370f8ef@redhat.com>

fgouget/spice,fgouget/spice,fgouget/spice,fgouget/spice