Update integ test to get the model name with method

Author: pinaraws

tests/integ/test_mxnet.py

@@ -97,7 +97,7 @@ def _deploy_estimator_and_assert_instance_type(estimator, instance_type):
             try:
                 predictor = estimator.deploy(1, instance_type)
 
-                model_name = predictor._model_names[0]
+                model_name = predictor._get_model_names()[0]
                 config_name = sagemaker_session.sagemaker_client.describe_endpoint(
                     EndpointName=predictor.endpoint_name
                 )["EndpointConfigName"]