only terminal response codes for x-ms-long-running-operation's

[ctaggart]

These changes pass all of the validation:

autorest --validation --azure-validator --use=@microsoft.azure/classic-openapi-validator@latest --use=@microsoft.azure/openapi-validator@latest --tag=package-2021-01-01-preview specification\vmware\resource-manager\readme.md
oav validate-spec specification\vmware\resource-manager\Microsoft.AVS\preview\2021-01-01-preview\vmware.json -p
oav validate-example specification\vmware\resource-manager\Microsoft.AVS\preview\2021-01-01-preview\vmware.json -p

I do not think we are supposed to put the async response codes in the spec. I think we are supposed to have the response codes for when the operation reaches its terminal provisioning state.

• Long Running Operations for Azure SDK
  https://github.com/Azure/adx-documentation-pr/blob/master/sdks/LRO/LRO_AzureSDK.md
• ProvisioningState property
  https://github.com/Azure/azure-resource-manager-rpc/blob/master/v1.0/Addendum.md#provisioningstate-property

This pull request is still in progress. I have not updated every affected operation.

[ctaggart]

I was wrong. The generated python code is checking the response codes from both the initial request and the polled requests against the set of response codes.