test: add an extra loop for slow udev initialization

test: add an extra loop for slow udev initialization

On slower machines, e.g. VMs, udev isn't fast enough to get the properties set
up by the time we're trying to get the device going. This fails when we try to
add the device with libinput_path_add_device().

We know that all litest devices will have ID_INPUT set, so check for that
before we continue.

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