Skip keras local mode test on gpu and use random port for serving in the test (aws#134)

* Skip keras local mode test on gpu

Author: icywang86rui

test/integration/local/test_keras.py

@@ -35,7 +35,7 @@ def test_keras_training(sagemaker_local_session, docker_image, tmpdir, framework
         entry_point=entry_point,
         role='SageMakerRole',
         train_instance_count=1,
-        train_instance_type=local_mode_instance_type,
+        train_instance_type='local',
         image_name=docker_image,
         sagemaker_session=sagemaker_local_session,
         model_dir='/opt/ml/model',