ui: dont show '__default__' in renderer

ui: dont show '__default__' in renderer

with the recent rework of the render/maps/arrays, we now
show 'Default (__default__)'. Since '__default__' is only an internal
value in the gui, don't expose it by explicitely checking for it

in the other render functions it works already because we either construct
the text differently (console_map) or we check the result from
parsing (vga_driver)

Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>