Re-implement sendToAll(gameOver) from server and add disconnected case
- restore the logic for the game over case
- distinguish the result of "fail" and "disconnect" so that we can figure out if the character is unexpectedly detected as out of the scene or the session is disconnected.
- in the current situation, even the session is disconnected, the "fail" result is shown. This makes us confuse to figure out what the root problem exactly is.