revise default data dir for inference in faster rcnn (#1636)

fluid/PaddleCV/faster_rcnn/README.md

@@ -128,7 +128,7 @@ Inference is used to get prediction score or image features based on trained mod
     python infer.py \
        --dataset=coco2017 \
         --pretrained_model=${path_to_pretrain_model}  \
-        --image_path=data/COCO17/val2017/  \
+        --image_path=dataset/coco/val2017/  \
         --image_name=000000000139.jpg \
         --draw_threshold=0.6
 

fluid/PaddleCV/faster_rcnn/README_cn.md

@@ -124,7 +124,7 @@ Faster RCNN 目标检测模型
     python infer.py \
        --dataset=coco2017 \
         --pretrained_model=${path_to_pretrain_model}  \
-        --image_path=data/COCO17/val2017/  \
+        --image_path=dataset/coco/val2017/  \
         --image_name=000000000139.jpg \
         --draw_threshold=0.6
 

fluid/PaddleCV/faster_rcnn/utility.py

@@ -127,7 +127,7 @@ def parse_args():
     add_arg('debug',            bool,   False,   "Debug mode")
     # SINGLE EVAL AND DRAW
     add_arg('draw_threshold',  float, 0.8,    "Confidence threshold to draw bbox.")
-    add_arg('image_path',       str,   'data/COCO17/val2017',  "The image path used to inference and visualize.")
+    add_arg('image_path',       str,   'dataset/coco/val2017',  "The image path used to inference and visualize.")
     add_arg('image_name',        str,    '',       "The single image used to inference and visualize.")
     # ce
     parser.add_argument(