Created by: luotao1

删单测的原因：

• paddle/fluid/inference/tests/book/下的预测单测，是使用老的预测C++接口（ @Xreki 设计 ）进行开发的，实际中的服务器端部署很早就使用了新接口，因此旧接口的单测可以删除。

删单测的其他好处：

• 这部分单测在WITH_COVERAGE=ON的情况下，占15G，占总体编译目录115G的13%。考虑到后期要做CI上的错误现场保留，编译目录需要逐步缩减。
• 能减少5分钟的时间

2020-05-09 14:59:38  1/37 Test #172: test_inference_image_classification_vgg ..............................   Passed   27.33 sec
2020-05-09 14:59:38       Start 173: test_inference_image_classification_resnet
2020-05-09 14:59:39  2/37 Test #170: test_api_impl ........................................................   Passed   28.51 sec
2020-05-09 14:59:39       Start 174: test_inference_label_semantic_roles
2020-05-09 15:00:05  3/37 Test #173: test_inference_image_classification_resnet ...........................   Passed   27.14 sec
2020-05-09 15:00:05       Start 175: test_inference_recognize_digits_mlp
2020-05-09 15:00:06  4/37 Test #174: test_inference_label_semantic_roles ..................................   Passed   26.86 sec
2020-05-09 15:00:06       Start 176: test_inference_recognize_digits_conv
2020-05-09 15:00:45  5/37 Test #175: test_inference_recognize_digits_mlp ..................................   Passed   40.07 sec
2020-05-09 15:00:45       Start 177: test_inference_recommender_system
2020-05-09 15:00:46  6/37 Test #176: test_inference_recognize_digits_conv .................................   Passed   40.12 sec
2020-05-09 15:00:46       Start 178: test_inference_word2vec
2020-05-09 15:01:12  7/37 Test #177: test_inference_recommender_system ....................................   Passed   26.81 sec
2020-05-09 15:01:12       Start 179: test_inference_nlp
2020-05-09 15:01:13  8/37 Test #178: test_inference_word2vec ..............................................   Passed   26.82 sec
2020-05-09 15:01:13       Start 226: test_train_recognize_digits_mlp
2020-05-09 15:01:16  9/37 Test #179: test_inference_nlp ...................................................   Passed    4.61 sec

https://xly.bce.baidu.com/paddlepaddle/paddle/ipipe/#/detail/893335/job/0