NIFI-5374 - Suppress stacktrace being returned to remote client when using NiFi REST API

[thenatog]

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[alopresto]

Reviewing...

[alopresto]

Thanks @thenatog. I reviewed this and it looks good. While initially I tried to run integration tests for the entire project, there is a failing integration test StandardControllerServiceProviderIT.testConcurrencyWithEnablingReferencingServicesGraph:96->testEnableReferencingServicesGraph which I opened a ticket for NIFI-5375. Building normally and then running integration tests on just this module is successful. I made some minor fixes for code style (see commit 8792f90 on branch NIFI-5374-PR-2840).

I verified against a running instance as well, and will merge this PR.