evdev: when the kernel fuzz is nonzero, set ours to zero

Our udev callout is supposed to reset the kernel fuzz to 0 and move the value to the LIBINPUT_FUZZ property. This is to stop the kernel from applying its own hysteresis-like approach.

Where the kernel fuzz is nonzero, something has gone wrong with that approach. Complain about it and set our fuzz to zero, we are in the hands of the kernel now. If we leave our fuzz as nonzero, we'll apply our own hysteresis on top of the kernel's and that leads to unresponsive behavior.

Fixes #313 (closed)