accidental styles piano and piano-cautionary gone berserk

[Antti Kaihola]

In 2.3.17, I suddenly get flats and sharps on every single flattened or
sharpened note, whereas in 2.2.0 the cautionaries occurred only where
the same note with different accidentals had appeared on another staff.

\relative es' { 
    #(set-accidental-style 'piano)
    es8 ges as bes as ges es ges | as bes as ges es ges as bes |
    % accidentals appear on every note!

    #(set-accidental-style 'piano-cautionary)
    as ges es ges as bes as ges | es ges as bes as ges es ges |
    % accidentals or cautionaries with parentheses on every note!
}