Make the script idempotent

scripts/disable-telemetry.ps1

@@ -7,18 +7,24 @@ Import-Module -DisableNameChecking $PSScriptRoot\..\lib\reg-helper.psm1
 
 echo "Adding telemetry domains to hosts file"
 $hosts = cat "$PSScriptRoot\..\res\telemetry-hosts.txt"
+$hosts_file = "$env:systemroot\System32\drivers\etc\hosts"
+
 [ipaddress[]] $ips = @()
 foreach ($h in $hosts) {
     try {
         # store for next part
         $ips += [ipaddress]$h
     } catch [System.InvalidCastException] {
-        # can be redirected by hosts
-        echo "0.0.0.0 $h" | Out-File -Encoding ASCII -Append "$env:systemroot\System32\drivers\etc\hosts"
+        $contaisHost = Select-String -Path $hosts_file -Pattern $h
+        If(-Not $contaisHost) {
+            # can be redirected by hosts
+            echo "0.0.0.0 $h" | Out-File -Encoding ASCII -Append $hosts_file
+        }
     }
 }
 
 echo "Adding telemetry ips to firewall"
+Remove-NetFirewallRule -ErrorAction SilentlyContinue -DisplayName "Block Telemetry IPs"
 New-NetFirewallRule -DisplayName "Block Telemetry IPs" -Direction Outbound `
     -Action Block -RemoteAddress ([string[]]$ips)