`test_container_create_with_vnet` fails: The subscription '00000000-0000-0000-0000-000000000000' could not be found

**Describe the bug**

`test_container_create_with_vnet` fails in CI:

https://dev.azure.com/azure-sdk/public/_build/results?buildId=1332811&view=logs&j=1e6fba43-bdcf-51f0-a062-3712c33fbb51&t=a1e787eb-ec67-5c3d-79ec-0c68f4f59d65&s=96ac2280-8cb4-5df5-99de-dd2da759617d

```
status_code = 404
response =
error_map = {401: , 404: , 409: }

def map_error(status_code, response, error_map):
if not error_map:
return
error_type = error_map.get(status_code)
if not error_type:
return
error = error_type(response=response)
> raise error
E azure.core.exceptions.ResourceNotFoundError: (SubscriptionNotFound) The subscription '00000000-0000-0000-0000-000000000000' could not be found.
E Code: SubscriptionNotFound
E Message: The subscription '00000000-0000-0000-0000-000000000000' could not be found.

/usr/lib64/az/lib/python3.6/site-packages/azure/core/exceptions.py:105: ResourceNotFoundError
------------------------------ Captured log call -------------------------------
WARNING msrest.serialization:serialization.py:187 Readonly attribute name will be ignored in class
WARNING msrest.serialization:serialization.py:185 polling is not a known attribute of class and will be ignored
WARNING msrest.serialization:serialization.py:185 location is not a known attribute of class and will be ignored
----------- generated xml file: /azure_cli_test_result/container.xml -----------
=========================== short test summary info ============================
FAILED tests/latest/test_container_commands.py::AzureContainerInstanceScenarioTest::test_container_create_with_vnet
```

This is a typical failure. See https://github.com/Azure/azure-cli/pull/17185.