sound/pipewire: stop threadloop before destroying context

During release(), the threadloop has to be stopped before the context is
destroyed, otherwise the threadloop continues to execute thus ending in
crashes due to SIGABRT or SIGSEGV.

Signed-off-by: Matias Ezequiel Vara Larsen <mvaralar@redhat.com>

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

@@ -503,6 +503,7 @@ impl AudioBackend for PwBackend {
         stream_hash.remove(&stream_id);
         stream_listener.remove(&stream_id);
         lock_guard.unlock();
+        self.thread_loop.stop();
         Ok(())
     }