Fix a few more multiplayer test timeouts

These can be tested by adding a `Task.Delay(3000);` at the end of the
`MultiplayerClient.JoinRoom` task. The reason is typically that
`Client.Room` becomes not-null but the join task still hasn't completed
yet, so e.g. the ready button is still disabled.

osu.Game.Tests/Visual/Multiplayer/TestSceneTeamVersus.cs

@@ -158,7 +158,7 @@ namespace osu.Game.Tests.Visual.Multiplayer
                 InputManager.Click(MouseButton.Left);
             });
 
-            AddUntilStep("wait for join", () => client.Room != null);
+            AddUntilStep("wait for join", () => multiplayerScreenStack.RoomManager.RoomJoined);
         }
     }
 }