(MODULES-7661) Fix JSON encoding for single object arrays

Previously the powershell tests were failing on tests where they returned a
single JSON object.  This is due to percularity in PowerShell where single
element arrays get reduced to just the item.  This commit changes the JSON
encoding to insert a begin and end bracket into the JSON string which forces the
output to be an array again.  This only applies for single elements not for
empty or multi element arrays.

tasks/update_history.ps1

@@ -76,7 +76,7 @@ Function Invoke-ExecuteTask($Detailed, $Title, $UpdateID, $MaximumUpdates) {
 
   $historyCount = $Searcher.GetTotalHistoryCount()
   if ($historyCount -gt $MaximumUpdates) { $historyCount = $MaximumUpdates }
-  $Searcher.QueryHistory(0, $historyCount) |
+  $Result = $Searcher.QueryHistory(0, $historyCount) |
     Where-Object { [String]::IsNullOrEmpty($Title) -or ($_.Title -match $Title) } |
     Where-Object { [String]::IsNullOrEmpty($UpdateID) -or ($_.UpdateIdentity.UpdateID -eq $UpdateID) } |
     ForEach-Object -Process {
@@ -110,7 +110,17 @@ Function Invoke-ExecuteTask($Detailed, $Title, $UpdateID, $MaximumUpdates) {
     }
 
     New-Object -TypeName PSObject -Property $props
-  } | ConvertTo-JSON
+  }
+
+  if ($Result -ne $null) {
+    if ($Result.GetType().ToString() -ne 'System.Object[]') {
+      '[ ' + ($Result | ConvertTo-JSON) + ' ]'
+    } else {
+      $Result | ConvertTo-JSON
+    }
+  } else {
+    '[ ]'
+  }
 }
 
 if (-Not $NoOperation) { Invoke-ExecuteTask -Detailed $Detailed -Title $Title -UpdateID $UpdateID -MaximumUpdates $MaximumUpdates }