Fix error check, log everything to agent log

Author: Chloe Hutchinson

packer/windows/conf/bin/bk-install-elastic-stack.ps1

@@ -172,7 +172,7 @@ nssm set buildkite-agent AppExit Default Restart
 If ($lastexitcode -ne 0) { Exit $lastexitcode }
 nssm set buildkite-agent AppRestartDelay 5000
 If ($lastexitcode -ne 0) { Exit $lastexitcode }
-nssm set buildkite-agent AppEvents Exit/Post "powershell C:\buildkite-agent\bin\terminate-instance.ps1"
+nssm set buildkite-agent AppEvents Exit/Post "powershell C:\buildkite-agent\bin\terminate-instance.ps1 3>&1 2>&1 > C:\buildkite-agent\buildkite-agent.log"
 If ($lastexitcode -ne 0) { Exit $lastexitcode }
 
 Restart-Service buildkite-agent

packer/windows/conf/buildkite-agent/scripts/terminate-instance.ps1

@@ -1,6 +1,3 @@
-# Stop script execution when a non-terminating error occurs
-$ErrorActionPreference = "Stop"
-
 Write-Output "terminate-instance: waiting for 10 seconds to allow agent logs to drain to Cloudwatch..."
 Start-Sleep -Seconds 10