Update cnn_tf.py to Tensorflow 2.0 and fix value error on cnn_tf.py

[Krishnagaanth]

Bro, Please Solve cnn_tf to tensorflow version 2.0
and fix the error
classifier.train(input_fn=train_input_fn, hooks=[logging_hook]):
TypeError: Value passed to parameter 'input' has DataType uint8 not in list of allowed values: float16, bfloat16, float32, float64, int32