Unexpected response when AzureBridge product doesn't exist

When I run Get-AzsAzureBridgeProduct as below, I get an unexpected response error:

```
PS C:\tasks\Azure\azurestack-powershell\src\Azs.AzureBridge.Admin\test> get-AzsAzureBridgeProduct -ActivationName "default" -ResourceGroupName "azurestack-activation" -Name "fakeproduct"

Get-AzsAzureBridgeProduct_Get: Unexpected response retrieving product information.
```

The error should say the resource does not exist, not an "unexpected response".