[Backport 2.15] Fix init encryption master key

[opensearch-trigger-bot]

Backport 487f33a from #2554

[ylwu-amzn]

Flaky test

Suite: Test class org.opensearch.ml.rest.RestMLFlowAgentIT
    {"error":{"reason":"System Error","details":"Memory Circuit Breaker is open, please check your resources!","type":"CircuitBreakingException"},"status":429}
  2> REPRODUCE WITH: gradlew ':opensearch-ml-plugin:integTest' --tests "org.opensearch.ml.rest.RestMLFlowAgentIT.testAgentCatIndexTool" -Dtests.seed=14CBBCEBA01403BB -Dtests.security.manager=false -Dtests.locale=tr -Dtests.timezone=America/Halifax -Druntime.java=21
  2> org.opensearch.client.ResponseException: method [POST], host [http://127.0.0.1:61821/], URI [/_plugins/_ml/agents/Ccc7GZABCRLEhl1XCtVE/_execute], status line [HTTP/1.1 429 Too Many Requests]
    {"error":{"reason":"System Error","details":"Memory Circuit Breaker is open, please check your resources!","type":"CircuitBreakingException"},"status":429}
        at __randomizedtesting.SeedInfo.seed([14CBBCEBA01403BB:CBF6C9EE85359E35]:0)
        at app//org.opensearch.client.RestClient.convertResponse(RestClient.java:376)
        at app//org.opensearch.client.RestClient.performRequest(RestClient.java:346)
        at app//org.opensearch.client.RestClient.performRequest(RestClient.java:321)
        at app//org.opensearch.ml.utils.TestHelper.makeRequest(TestHelper.java:181)
        at app//org.opensearch.ml.utils.TestHelper.makeRequest(TestHelper.java:154)
        at app//org.opensearch.ml.rest.RestMLFlowAgentIT.executeAgent(RestMLFlowAgentIT.java:131)
        at app//org.opensearch.ml.rest.RestMLFlowAgentIT.executeAgentCatIndexTool(RestMLFlowAgentIT.java:110)
        at app//org.opensearch.ml.rest.RestMLFlowAgentIT.testAgentCatIndexTool(RestMLFlowAgentIT.java:41)