Plug Autorest.Python testsuite in azure-core testing

[lmazuel]

In order to correctly test azure-core, the autorest.python testsuite should be pulled and done here, like today for msrest:
https://github.com/Azure/msrest-for-python/blob/0732bc90bdb290e5f58c675ffdd7dbfa9acefc93/.travis.yml#L12-L19

[lmazuel]

This was done and this issue was forgotten to be closed. We have an autorest job now. CC @praveenkuttappan @scbedd