test: set the abs resolution after creating the device

test: set the abs resolution after creating the device

Until uinput gets that capability (likely not before 3.17) all we can do is a
racy approach of setting it after creating it. That won't work well for
anything test where libinput is already listening to udev when the device is
created, but it does work for those cases where libinput is started after the
device was initialized.

And it's a better alternative than not testing anything dependent on
resolution settings.

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>