Register-AzAutomationDscNode does not support Linux VMs

## Description
Register-AzAutomationDscNode does not support Linux VMs

## Steps to reproduce
1. Target a Linux VM and run Register-AzAutomationDscNode
2. See that Node Registration fails

## Environment data

```
Name Value
---- -----
PSVersion 7.1.3
PSEdition Core
GitCommitId 7.1.3
OS Microsoft Windows 10.0.19043
Platform Win32NT
PSCompatibleVersions {1.0, 2.0, 3.0, 4.0…}
PSRemotingProtocolVersion 2.3
SerializationVersion 1.1.0.1
WSManStackVersion 3.0
```

## Module versions

```powershell
Get-Module az.automation -listavailable

Directory: C:\Program Files\WindowsPowerShell\Modules

ModuleType Version PreRelease Name PSEdition ExportedCommands
---------- ------- ---------- ---- --------- ----------------
Script 1.5.2 Az.Automation Core,Desk {Get-AzAutomationHybridWorkerGroup, Remove-AzAutomationHybridWorkerGroup, Get-AzAutomationJobOutputRecord,
```

## Debug output

```

```

## Error output

```
RequestId :
Message : Long running operation failed with status 'Failed'. Additional Info:'At least one resource deployment operation failed. Please list deployment operations for details. Please see https://aka.ms/DeployOperations for usage details.'
ServerMessage : DeploymentFailed: Long running operation failed with status 'Failed'. Additional Info:'At least one resource deployment operation failed. Please list deployment operations for details. Please see https://aka.ms/DeployOperations for usage details.' (System.Collections.Generic.List`1[Microsoft.Rest.Azure.CloudError])
ServerResponse : {OK}
RequestMessage : {GET https://management.azure.com/subscriptions/8f210ae2-823d-44e2-a9ac-d059254e8645/resourcegroups/CHAIRLIFT-INTEGRATIONTESTS/providers/Microsoft.Resources/deployments/13b327b2-ce88-46c4-a944-917f3faf9a37/operationStatuses/08585770708871288837?api-version=2018-05-01}
InvocationInfo : {Register-AzAutomationDscNode}
Line : $null = Register-AzAutomationDscNode @params -Erroraction 'Stop'

Position : At C:\Program Files\WindowsPowerShell\Modules\StigRepo\1.3\module\AzureFunctions.ps1:1233 char:21
+ … $null = Register-AzAutomationDscNode @params -Erroraction 'Stop'
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
StackTrace : at Microsoft.Rest.ClientRuntime.Azure.LRO.AzureLRO`2.CheckForErrors()
at Microsoft.Rest.ClientRuntime.Azure.LRO.PutLRO`2.CheckForErrors()
at Microsoft.Rest.ClientRuntime.Azure.LRO.AzureLRO`2.StartPollingAsync()
at Microsoft.Rest.ClientRuntime.Azure.LRO.AzureLRO`2.BeginLROAsync()
at Microsoft.Rest.Azure.AzureClientExtensions.GetLongRunningOperationResultAsync[TBody,THeader](IAzureClient client, AzureOperationResponse`2 response, Dictionary`2 customHeaders, CancellationToken cancellationToken)
at Microsoft.Rest.Azure.AzureClientExtensions.GetLongRunningOperationResultAsync[TBody](IAzureClient client, AzureOperationResponse`1 response, Dictionary`2 customHeaders, CancellationToken cancellationToken)
at Microsoft.Rest.Azure.AzureClientExtensions.GetPutOrPatchOperationResultAsync[TBody](IAzureClient client, AzureOperationResponse`1 response, Dictionary`2 customHeaders, CancellationToken cancellationToken)
at Microsoft.Azure.Management.Internal.ResourceManager.Version2018_05_01.DeploymentsOperations.CreateOrUpdateWithHttpMessagesAsync(String resourceGroupName, String deploymentName, Deployment parameters, Dictionary`2 customHeaders, CancellationToken cancellationToken)
HistoryId : 7
```

Start by reproducing Register-AzAutomationDscNode against a Linux VM with the reported Az.Automation 1.5.2 and inspect the cmdlet's node-registration path. Done means the command completes successfully and registers the Linux node instead of returning the reported deployment failure.

Written by the indexing model from the issue text.