Created by: emailweixu

When the define_py_data_sources2 has both train_list and test_list, for job=test, the trainer will create both dataProvider_ and testDataProvider_. But dataProvider_ is not used. This causes SIGSEGV at finishAsync() because asyncLoader_ is not created.

Change-Id: If579f715f80a70ebc795094792c3436bfa0f5746