Fix tests on downlevel systems failing at end of test (microsoft#2177)

* Try to debug tests failing at end

* Disable logging

* More printing

* Smore

* Another test

* Final fix

* Only 0 out last exit code once

scripts/install-test-certificates.ps1

@@ -15,6 +15,10 @@ param (
     [Parameter(Mandatory = $true)]
     [string]$OutputFile = ""
 )
+
+Set-StrictMode -Version 'Latest'
+$PSDefaultParameterValues['*:ErrorAction'] = 'Stop'
+
 [System.DateTimeOffset]$NotBefore = [System.DateTimeOffset]::Now.AddDays(-1)
 [System.DateTimeOffset]$NotAfter = [System.DateTimeOffset]::Now.AddDays(365)
 
@@ -174,7 +178,7 @@ $Leaf = CreateLeafCert $IntermediateSigner
 
 $Collection = [System.Security.Cryptography.X509Certificates.X509Certificate2Collection]::new()
 
-$Collection.Add($Leaf[1]) # TODO(AnRossi):Why is $Leaf an array of an Int and the Cert?
+$Collection.Add($Leaf[1]) | Out-Null # TODO(AnRossi):Why is $Leaf an array of an Int and the Cert?
 #Export the intermediate and root certs and then import them to drop their private keys.
 $Collection.Import($IntermediateSigner.rawData)
 $Collection.Import($Root.rawData)

scripts/log.ps1

@@ -145,6 +145,7 @@ function Log-Cancel {
             wpr.exe -cancel -instancename $InstanceName 2>&1
         } catch {
         }
+        $global:LASTEXITCODE = 0
     } elseif ($IsMacOS) {
     } else {
         if (!(Test-Path $TempDir)) {