Always install demo certs if configured with demo certs

[cwperks]

Description

This PR updates the demo installer to always install the demo certs into the config/ folder even if the following settings are already present in opensearch.yml

/**
  * plugins.security.ssl.transport.pemcert_filepath: esnode.pem
  * plugins.security.ssl.transport.pemkey_filepath: esnode-key.pem
  * plugins.security.ssl.transport.pemtrustedcas_filepath: root-ca.pem
  * plugins.security.ssl.http.pemcert_filepath: esnode.pem
  * plugins.security.ssl.http.pemkey_filepath: esnode-key.pem
  * plugins.security.ssl.http.pemtrustedcas_filepath: root-ca.pem
  */

By ensuring that the files are always copied, it resolves an issue seen in the helm-charts repo where the values are already present in opensearch.yml but the certs are not written to the config/ folder in the event that the opensearch process dies on one of the pods and is replaced. The reason for that is that it goes through the installation script and aborts saying that security is already configured.

Issues Resolved

Resolves: opensearch-project#5044

Helm Charts: opensearch-project/helm-charts#680

Check List

• New functionality includes testing
• New functionality has been documented
• New Roles/Permissions have a corresponding security dashboards plugin PR
• API changes companion pull request created
• Commits are signed per the DCO using --signoff

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