genisoimage is needed for running the tests/qtest/cdrom-test qtest.

Signed-off-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-Id: <20201006174347.152040-1-thuth@redhat.com>
Message-Id: <20201007160038.26953-7-alex.bennee@linaro.org>