test/rauc.t: fix non-service test
test/rauc.t: fix non-service test

The image files were only created for the service case. Create them in the test
case for now.

Signed-off-by: Jan Luebbe <3a82f1ac4ad59607a20f180f1c67ac8ba31ad0d5@pengutronix.de>

ejoerns/rauc,jluebbe/rauc,rauc/rauc,jluebbe/rauc,rauc/rauc,jluebbe/rauc,ejoerns/rauc,ejoerns/rauc,rauc/rauc