test: print strerror() if uinput device creation fails

test: print strerror() if uinput device creation fails

The most common error running the test suite is not running as root, but the
error message is hard to interpret. Make it more explicit when it failed,
printing the strerror of the errno.

Note that libevdev 1.3 is needed to get EACCES instead of EBADF
http://cgit.freedesktop.org/libevdev/commit/?id=debe9b030c8069cdf78307888ef3b65830b25122
A workaround is put in place for now until libevdev 1.3 is commonplace.

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>