run.log_table stores 1-item lists differently

The following code:
```
run.log_table('test',value={'x':['asd','sdf'],'y':[1,2]})
run.log_table('test1',value={'x':['asd'],'y':[1]})
run.get_metrics()
```
will yield:
`{'test': {'x': ['asd', 'sdf'], 'y': [1, 2]}, 'test1': {'x': 'asd', 'y': 1}}`

It shows that single-item lists are stored differently than lists with multiple items.

This makes the JSON produced from these inconsistent types hard to parse down the line (e.g. outside of AML as in PowerBI for example).

If we pass in a list, we would expect that it is stored as a list even if there is only one item in the list.

---
#### Document Details

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* ID: 2e24ac95-7027-6a3c-81e6-f20cc4415219
* Version Independent ID: 9498cdc2-0d04-39a3-08ce-ef9ea8f2d153
* Content: [azureml.core.run.Run class - Azure Machine Learning Python](https://docs.microsoft.com/en-us/python/api/azureml-core/azureml.core.run.run?view=azure-ml-py)
* Content Source: [AzureML-Docset/stable/docs-ref-autogen/azureml-core/azureml.core.run.Run.yml](https://github.com/MicrosoftDocs/MachineLearning-Python-pr/blob/live/AzureML-Docset/stable/docs-ref-autogen/azureml-core/azureml.core.run.Run.yml)
* Service: **machine-learning**
* Sub-service: **core**
* GitHub Login: @debfro
* Microsoft Alias: **debfro**

Comece reproduzindo as chamadas fornecidas para Run.log_table e Run.get_metrics no contexto do Azure Machine Learning Python SDK. Rastreie como listas de um único item são representadas nas métricas e no JSON retornados e, em seguida, adicione cobertura mostrando que listas de um único item passadas explicitamente permanecem listas.

Escrita pelo modelo de indexação a partir do texto da issue.