fix: cloudtrail creation conditional (#129)

after the `existing_cloudtrail_config` refactor the `deploy_cloudtrail`
flag was not correctly setup

<!--
Thank you for your contribution!

## General recommendations
Check contribution guidelines at
https://github.com/sysdiglabs/terraform-aws-secure-for-cloud/blob/master/CONTRIBUTE.md#contribution-checklist

For a cleaner PR make sure you follow these recommendations:
- Review modified files and delete small changes that were not intended
and maybe slip the commit.
- Use Pull Request Drafts for visibility on Work-In-Progress branches
and use them on daily mob/pairing for team review
- Unless an external revision is desired, in order to validate or gather
some feedback, you are free to merge as long as **validation checks are
green-lighted**

## Checklist

- [ ] If `test/fixtures/*/main.tf` files are modified. I have updated:
    - [ ] the snippets in the README.md file under root folder.
- [ ] the snippets in the README.md file for the corresponding example.
- [ ] If `examples` folder are modified. I have updated:
    - [ ] README.md file with pertinent changes.
- [ ] `test/fixtures/*/main.tf` in case the snippet needs modifications.
- [ ] If any architectural change has been made, I have updated the
diagrams.

-->

Author: iru

examples/organizational/cloudtrail.tf

@@ -1,5 +1,6 @@
 locals {
-  deploy_cloudtrail  = var.existing_cloudtrail_config == null || var.existing_cloudtrail_config.cloudtrail_sns_arn == "create" || var.existing_cloudtrail_config.cloudtrail_sns_arn == null
+  deploy_cloudtrail = var.existing_cloudtrail_config == null || (var.existing_cloudtrail_config != null && var.existing_cloudtrail_config.cloudtrail_sns_arn == "create" && var.existing_cloudtrail_config.cloudtrail_s3_sns_sqs_arn == null)
+
   cloudtrail_sns_arn = local.deploy_cloudtrail ? module.cloudtrail[0].cloudtrail_sns_arn : var.existing_cloudtrail_config.cloudtrail_sns_arn
   cloudtrail_s3_arn  = local.deploy_cloudtrail ? module.cloudtrail[0].s3_bucket_arn : var.existing_cloudtrail_config.cloudtrail_s3_arn
 }