Update backup.ps1

Fixing issue 271

PowerFGT/Public/monitor/system/config/backup.ps1

@@ -1,4 +1,4 @@
-#
+#
 # Copyright 2022, Alexis La Goutte <alexis dot lagoutte at gmail dot com>
 #
 # SPDX-License-Identifier: Apache-2.0
@@ -42,28 +42,29 @@ function Get-FGTMonitorSystemConfigBackup {
 
     Process {
 
+        $scope="global"
         $invokeParams = @{ }
         if ( $PsBoundParameters.ContainsKey('skip') ) {
             $invokeParams.add( 'skip', $skip )
         }
         if ( $PsBoundParameters.ContainsKey('vdom') ) {
             $invokeParams.add( 'vdom', $vdom )
+            $scope="vdom"
         }
 
         #before 7.6.x, config/backup is available with get method and using paramater
         if ($connection.version -lt "7.6.0") {
             $method = "get"
-            $uri = 'api/v2/monitor/system/config/backup?scope=global'
+            $uri = "api/v2/monitor/system/config/backup?scope=$scope"
             $body = ""
         }
         else {
             $method = "post"
             $uri = 'api/v2/monitor/system/config/backup'
             $body = @{
-                "scope" = "global"
+                "scope" = "$scope"
             }
         }
-
         $response = Invoke-FGTRestMethod -uri $uri -method $method -body $body -connection $connection @invokeParams
         $response
     }