fixed asking all network clients to "play again" after unsolved game end

fixed asking all network clients to "play again" after unsolved game end

Before, all network clients were asked to play again after a game was
lost, which could cause problems (or at least confusion) when starting
a new network game from different network clients at the same time.

Now, only the network client which started the network game is asked
to play again, while all other clients only confirm that the game is
over and return to the main menu.