Bug#584752: same for keymap selection

[Adam Borowski <kilobyte@angband.pl>]

Same for the keymap selection screen: if you select a wrong one, the
<go back> button doesn't work.

(Also, it's strange that typing "po" selects "Persian" instead of "Polish"
-- one would expect that if a prefix search doesn't work, it'd go to "O"
instead).

-- 
“This is gonna be as easy as cheating on an ethics exam!”
    -Cerise Brightmoon