test: ignore test devices, or real devices during test suite runs

[whot]

Set an option on all our created uinput devices, and an environment variable when we're running the test suite. If both of these are set we process the device, otherwise ignore the device during PreInit.

This stops the driver picking up events from test suite runs (potentially clicking around on the desktop) and it stops the test suite from false positives by locally connected devices.

[skomra]

Reviewed-by: Aaron Skomra aaron.skomra@wacom.com