fix openvino python demo (Megvii-BaseDetection#169)

* fix openvino python demo

Author: Joker316701882

demo/OpenVINO/python/openvino_inference.py

@@ -150,7 +150,7 @@ def main():
                          conf=args.score_thr, class_names=COCO_CLASSES)
 
     mkdir(args.output_dir)
-    output_path = os.path.join(args.output_dir, args.image_path.split("/")[-1])
+    output_path = os.path.join(args.output_dir, args.input.split("/")[-1])
     cv2.imwrite(output_path, origin_img)