Jonas Dreßler authored Dec 12, 2019 and Benjamin Berg committed Dec 12, 2019

With cd051e6c we added another method
for setting the display brightness, it was forgotten there to convert
the actual brightness value to a percentage when setting the GTask
return value.

Since this return value is used to display the brightness OSD in
gsd-media-keys-manager, we ended up with values above 100% shown in the
brightness OSD. Fix that by adjusting the return value to be a
percentage.