A short red wheel is displayed after the LED countdown has been
completed. It prevents a new countdown from starting, or night mode to
be activated.

Since a red wheel is displayed at the start of the calibration process
anyway (until measurements are stable enough), it should hopefully not
be too surprising.

* The 'int' return signature and the comment
'Returns the number of remaining leds' sounds like the
function would return its current countdown state.
However, it only returns the number of remaining
leds after the button was released. Thus change
the type to 'bool' and return 'true' after a
successful countdown

* Do not use 1 as return value for night mode,
because it is ambigous. Return 'false' instead.