disable mp::configure in mp transient in networked mp

This was only executed on the host. And it didn't work in networked mp because the other clients didn't expect this, and proceeded to the next scenario immediately.
That's why i disabled it in networked mp.

src/playcampaign.cpp

@@ -627,7 +627,7 @@ LEVEL_RESULT play_game(game_display& disp, game_state& gamestate,
 					connect_engine(new mp::connect_engine(disp, gamestate,
 						params, !network_game, false));
 
-				if (allow_new_game_flag || game_config::debug) {
+				if (allow_new_game_flag || (game_config::debug && network::nconnections() == 0)) {
 					// Opens mp::connect dialog to allow users to
 					// make an adjustments for scenario.
 					mp::ui::result connect_res = mp::goto_mp_connect(disp,