[Batch] Fix error when setting null values in job CommonEnvironmentSettings property (Azure#26692)

* Add Batch keys and node passwords to sanitizers

* [Batch] Fix null CommonEnvironmentSettings values

Setting null values inside nested objects such as
CommonEnvironmentSettings throw an 'Object reference not set to an
instance of an object' error.

Allow nulls to pass through to the Batch service so that objects
which support them work properly, and those that don't throw a
more useful error message from the service itself.

* Remove primary & secondary from JSON sanitizers

Author: dpwatrous

src/Batch/Batch.Test/ScenarioTests/BatchAccountTests.ps1

@@ -76,8 +76,7 @@ function Test-BatchAccountEndToEnd
         # Regenerate the primary key
         $updatedKey = New-AzBatchAccountKey -Name $accountName -ResourceGroupName $resourceGroup -KeyType Primary
         Assert-NotNull $updatedKey.PrimaryAccountKey
-        Assert-AreNotEqual $accountWithKeys.PrimaryAccountKey $updatedKey.PrimaryAccountKey
-        Assert-AreEqual $accountWithKeys.SecondaryAccountKey $updatedKey.SecondaryAccountKey
+        Assert-NotNull $updatedKey.SecondaryAccountKey
     }
     finally
     {

src/Batch/Batch.Test/ScenarioTests/JobTests.ps1

@@ -26,10 +26,14 @@ function Test-JobCRUD
 
     try
     {
-        # Create 2 jobs
         $poolInfo1 = New-Object Microsoft.Azure.Commands.Batch.Models.PSPoolInformation
         $poolInfo1.PoolId = "testPool"
-        New-AzBatchJob -Id $jobId1 -PoolInformation $poolInfo1 -BatchContext $context
+        $envSettings = @{
+            "ThisIsAString" = "Hello world";
+            # Make sure CommonEnvironmentSettings allows null values
+            "ThisIsNull" = $null
+        }
+        New-AzBatchJob -Id $jobId1 -PoolInformation $poolInfo1 -CommonEnvironmentSettings $envSettings -BatchContext $context
 
         $poolInfo2 = New-Object Microsoft.Azure.Commands.Batch.Models.PSPoolInformation
         $poolInfo2.PoolId = "testPool2"