Update Validate-NDESUrl.ps1 (#145)

$testChallenge =  $null is to reset $testChallenge when running it multiple times.
$testChallenge gets compounded when running it multiple times in ISE, causing incorrect test & result

Author: WplusAzureAuto

CertificationAuthority/Validate-NDESUrl.ps1

@@ -303,7 +303,8 @@ Write-host
 Write-Host "Using a query size of $($querysize)KB... "
 Write-Host
 $challengeBase = "NDESLongUrlValidatorFakeChallengeNDESLongUrlValidatorFakeChallengeNDESLongUrlValidatorFakeChallengeNDESLongUrlValidatorFakeChallengeNDESLongUrlValidatorFakeChallengeNDESLongUrlValidatorFakeChallengeNDESLongUrlValidatorFakeChallengeNDESLongUrlValidatorFakeChallengeNDESLongUrlValidatorFakeChallengeNDESLongUrlValidatorFakeChallengeNDESLongUrlValidatorFakeChallengeNDESLongUrlValidatorFakeChallengeNDESLongUrlValidatorFakeChallengeNDESLongUrlValidatorFakeChallengeNDESLongUrlValidatorFakeChallengeNDESLongUrlValidatorFakeChallengeNDESLongUrlValidatorFakeChallengeNDESLongUrlValidatorFakeChallengeNDESLongUrlValidatorFakeChallengeNDESLongUrlValidatorFakeChallengeNDESLongUrlValidatorFakeChallengeNDESLongUrlValidatorFakeChallengeNDESLongUrlValidatorFakeChallengeNDESLongUrlValidatorFakeChallengeNDESLongUrlValidatorFakeChallengeNDESLongUrlValidatorFakeChallengeNDESLongUrlValidatorFakeChallengeNDESLongUrlValidatorFakeChallengeNDESLongUrlValidatorFakeChallengeNDESLongUrlValidatorFakeChallengeNDESLongUrlValidatorFakeChallenge";
-            
+$testChallenge = $null
+
     for ($i=1; $i -le $querySize; $i++){         
 
         $testChallenge += $challengeBase + ($i + 1)
@@ -354,4 +355,4 @@ Write-Host
 write-host "Ending script..." -ForegroundColor Yellow
 Write-host 
 
-#endregion
+#endregion