create new DeviceListReceived event to avoid race conditions in short–lived client applications

buttplug/src/client/client_event_loop.rs

@@ -314,6 +314,7 @@ where
           let device = self.create_client_device(d);
           self.send_client_event(ButtplugClientEvent::DeviceAdded(device));
         }
+        self.send_client_event(ButtplugClientEvent::DeviceListReceived);
         true
       }
     }

buttplug/src/client/mod.rs

@@ -128,6 +128,9 @@ pub enum ButtplugClientEvent {
   /// Emitted when a device has been removed from the server. Includes a
   /// [ButtplugClientDevice] object representing the device.
   DeviceRemoved(Arc<ButtplugClientDevice>),
+  /// Emitted when the device list is received as a response to a
+  /// DeviceListRequest call, which is sent during the handshake.
+  DeviceListReceived,
   /// Emitted when a client has not pinged the server in a sufficient amount of
   /// time.
   PingTimeout,

buttplug/tests/test_client.rs

@@ -142,6 +142,10 @@ async fn test_client_scanning_finished() {
   let (client, _) = test_client_with_device().await;
   let mut recv = client.event_stream();
   assert!(client.start_scanning().await.is_ok());
+  assert!(matches!(
+    recv.next().await.expect("Test, assuming infallible."),
+    ButtplugClientEvent::DeviceListReceived
+  ));
   assert!(matches!(
     recv.next().await.expect("Test, assuming infallible."),
     ButtplugClientEvent::ScanningFinished