Fix the config_parse.py if user does not set padding in the old config.

python/paddle/trainer/config_parser.py

@@ -815,9 +815,9 @@ class Pool(Cfg):
                  size_y=None,
                  img_width=None,
                  start=None,
-                 stride=None,
+                 stride=1,
                  stride_y=None,
-                 padding=None,
+                 padding=0,
                  padding_y=None):
         self.add_keys(locals())
 
@@ -1111,9 +1111,9 @@ def parse_pool(pool, input_layer_name, pool_conf):
 
     config_assert(not pool.start, "start is deprecated in pooling.")
 
-    if pool.padding is not None:
     pool_conf.padding = pool.padding
     pool_conf.padding_y = default(pool.padding_y, pool_conf.padding)
+
     pool_conf.output_x = cnn_output_size(
         pool_conf.img_size, pool_conf.size_x, pool_conf.padding,
         pool_conf.stride, False)