预处理batch动作设置drop_remainder

跟随训练脚本逻辑，找到数据预处理文件：official/vision/image_classification/resnet/imagenet_preprocessing.py。

在数据读取函数“input_fn”内部设置drop_remainder为True，该迁移点完成。

def input_fn(is_training,
             data_dir,
             batch_size,
             dtype=tf.float32,
             datasets_num_private_threads=None,
             parse_record_fn=parse_record,
             input_context=None,
             drop_remainder=False,
             tf_data_experimental_slack=False,
             training_dataset_cache=False,
             filenames=None):
……

Returns:
  A dataset that can be used for iteration.
"""
drop_remainder=True

if filenames is None:
  filenames = get_filenames(is_training, data_dir)
dataset = tf.data.Dataset.from_tensor_slices(filenames)