call equals on formatted strings since they will never be null

[tsturzl]

(If this PR fixes a github issue, please add Fixes #<xyz>.)

Fixes #1210

Motivation

When running with TLS disabled PulsarServiceLookupHandler::isLookupMQTTBroker is calling localBrokerData.getPulsarServiceUrlTls() which returns null if TLS is disabled. This method then tried to call equals(..) on the returned value which is null causing a NullPointerException. This prevents MoP proxy from working properly, as it will never resolve the host and this loop will simply crash.

Modifications

Instead of calling equals on the values returned from localBrokerData, which can be null if missing in the metadata store, I instead call equals on the strings created which are compared against since those will never be null, but it's safe to pass null as an argument to String::equals. This prevents the NullPointerException with minimal change.

Verifying this change

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• Added integration tests for end-to-end deployment with large payloads (10MB)
• Extended integration test for recovery after broker failure

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[github-actions]

@tsturzl:Thanks for your contribution. For this PR, do we need to update docs?
(The PR template contains info about doc, which helps others know more about the changes. Can you provide doc-related info in this and future PR descriptions? Thanks)