image-fuzzer: Public API for image-fuzzer/runner/runner.py

__init__.py provides the public API required by the test runner
Reviewed-by: NStefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: NMaria Kustova <maria.k@catit.be>
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>

tests/image-fuzzer/qcow2/__init__.py

+from layout import create_image