There is no error message in response while failing to create app service plan

Symptom:
After tested, I found that there is no error message in response, no error message in ServiceError and no StatusCode since they all are nil while failing to create app service plan. It should return the error message in response.

Rest api call:
```
PUT https://management.azure.com/subscriptions/xx-xx-xx-xx/resourceGroups/example-asp-resources/providers/Microsoft.Web/serverfarms/api-appserviceplan-pro

{
"kind": "Linux",
"location": "eastus2",
"properties": {
"reserved": true,
"isXenon": false
},
"sku": {
"name": "I3",
"tier": "Isolated",
"size": "I3",
"capacity": 1
},
"tags": {}
}
```

Result:

Start by reproducing the shown PUT request for the Azure app service plan and inspect the failure response, ServiceError, and StatusCode handling. Trace the relevant REST API specification and error response definitions; done means a failed create request returns the error message and populated error metadata instead of nil values.

Written by the indexing model from the issue text.