DatasetConsumptionConfig and PipelineParameter cannot be reused

Following the tutorial to create ML datasets as pipeline parameters:
https://github.com/Azure/MachineLearningNotebooks/blob/master/how-to-use-azureml/machine-learning-pipelines/intro-to-pipelines/aml-pipelines-showcasing-dataset-and-pipelineparameter.ipynb

This requires the creation of PipelineParameter and then DatasetConsumptionConfig objects.
If you have multiple steps which require the same dataset input, you would expect to be able to use the same PipelineParameter for all the steps. However when that PipelineParameter is used with a DatasetConsumptionConfig this doesn't work.

When building the pipeline we get the error:
`'PipelineDataset' object has no attribute '_get_datapath'`

Seems the object is altered when it is used, so when we use it a second time it breaks.

The work around at the moment is to create a new PipelineParameter for every step that uses the dataset, hence the number of pipeline parameters to configure grows very fast.

Tail end of error log (can't copy/paste text)

從連結的教學課程 aml-pipelines-showcasing-dataset-and-pipelineparameter.ipynb 開始，使用一個 PipelineParameter 和多個 DatasetConsumptionConfig 物件重現該 pipeline。追蹤回報的「_get_datapath」錯誤附近的 pipeline 建構過程。當相同的資料集輸入可以在多個步驟之間重複使用，且 pipeline 建構成功時，即視為完成。

由索引模型根據 Issue 內容生成。