[Windows] Use common approach to set machine vars (#8830)

images/windows/scripts/helpers/ImageHelpers.psm1

@@ -19,7 +19,6 @@ Export-ModuleMember -Function @(
     'Add-DefaultItem'
     'Get-SystemVariable'
     'Get-DefaultVariable'
-    'Set-SystemVariable'
     'Set-DefaultVariable'
     'Install-Binary'
     'Install-VisualStudio'

images/windows/scripts/helpers/PathHelpers.ps1

@@ -54,16 +54,6 @@ function Get-DefaultVariable {
     [System.GC]::Collect()
 }
 
-function Set-SystemVariable {
-    param(
-        [string]$SystemVariable,
-        [string]$Value
-    )
-    
-    [System.Environment]::SetEnvironmentVariable($SystemVariable, $Value, "Machine")
-    Get-SystemVariable $SystemVariable
-}
-
 function Set-DefaultVariable {
     param(
         [string]$DefaultVariable,
@@ -93,7 +83,7 @@ function Set-MachinePath {
         [string]$NewPath
     )
     
-    Set-SystemVariable PATH $NewPath
+    [System.Environment]::SetEnvironmentVariable("PATH", $NewPath, "Machine")
 }
 
 function Set-DefaultPath {

images/windows/scripts/helpers/test/PathHelpers.Tests.ps1

@@ -25,10 +25,3 @@ Describe "Add-MachinePathItem Tests"{
         Add-MachinePathItem -PathItem 'C:\baz' | Should Be 'C:\baz;C:\foo;C:\bar'
     }
 }
-
-Describe 'Set-SystemVariable Tests' {
-    Mock Set-ItemProperty {return}
-    It 'Set-SystemVariable should return new path' {
-        Set-SystemVariable -SystemVariable "NewPathVar" -Value "C:\baz" | Should Be "C:\baz"
-    }
-}