Fixes demo installer to not use the deprecated System.setSecurityManager() #5262
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Description
With recent baseline to 21 and update to JSM, the CI failed with test failures for demo config setup tests. This PR addresses those by implementing a custom exit handler.
Issues Resolved
#5261
Testing
Check List
- [ ] New functionality has been documented- [ ] New Roles/Permissions have a corresponding security dashboards plugin PR- [ ] API changes companion pull request createdBy submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.
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