qdl: make interfaces Sync

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>

qemu-rdw/src/clipboard.rs

@@ -107,7 +107,7 @@ impl Handler {
                                     Err(qdl::Error::Failed(format!("{}", e)))
                                 }
                             };
-                            let _ = tx.send(reply);
+                            let _ = tx.lock().unwrap().send(reply);
                         });
                     }
                 }