sound/pipewire: destroy multiple pipewire streams that are not destroyed

The PCM command transition prepare->prepare or set_param->prepare
is allowed by the specification. however this type of transition
in pipewire lead to multiple creation of pipewire streams that are
not destroyed. This PR ensures that in a case like this,
when the prepare fn() in the pipewire backend is called multiple
times without the release fn(), there should be only one pipewire stream.

Close rust-vmm#490

Signed-off-by: Dorinda Bassey <dbassey@redhat.com>

vhost-device-sound/src/audio_backends/pipewire.rs

@@ -208,6 +208,12 @@ impl AudioBackend for PwBackend {
 
             let params = &stream_params[stream_id as usize].params;
 
+            if let Some(stream) = stream_hash.get(&stream_id) {
+                stream.disconnect().expect("could not disconnect stream");
+                stream_hash.remove(&stream_id);
+                stream_listener.remove(&stream_id);
+            }
+
             let mut pos: [u32; 64] = [SPA_AUDIO_CHANNEL_UNKNOWN; 64];
 
             match params.channels {