Some minor lobby ui improvements.

Set up the defaults to better match what's needed in the main lobby
causing less resizing after joining. Also avoid some silly cases.

- Never show a horizontal scrollbar for the rooms and lobby list.

- Always show it for the game list.

- Hide it for the rooms (always might be slightly better).

data/gui/default/window/lobby_main.cfg

@@ -100,6 +100,7 @@
 	id = "game_list"
 	definition = "default"
 
+	vertical_scrollbar_mode = "always"
 	[header]
 		[row]
 			[column]
@@ -330,6 +331,8 @@
 			horizontal_grow = "true"
 			vertical_grow = "true"
 			[scrollbar_panel]
+				horizontal_scrollbar_mode = "never"
+				vertical_scrollbar_mode = "auto"
 				[definition]
 					{ONE_PLAYERLISTBOX "active_game" _"Selected game"}
 					{ONE_PLAYERLISTBOX "active_room" _"Current room"}
@@ -356,6 +359,8 @@
 [listbox]
 	id = "room_list"
 	definition = "default"
+
+	horizontal_scrollbar_mode = "never"
 	[header]
 		[row]
 			[column]