tests: acpi: silence applesmc warning about invalid key

tests: acpi: silence applesmc warning about invalid key

OSK value is irrelevant for ACPI test case.
Supply fake OSK explicitly to prevent QEMU complaining about
invalid key when it fallbacks to default_osk.

Suggested-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Igor Mammedov <imammedo@redhat.com>
Message-Id: <20220728133713.1369596-1-imammedo@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>