KAFKA-5173: Add logging to dump JaasContext before writing it to file

[baluchicken]

@rajinisivaram plz review.

[asfbot]

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Test FAILed (JDK 8 and Scala 2.12).

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Test FAILed (JDK 8 and Scala 2.11).

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Test FAILed (JDK 7 and Scala 2.10).

[rajinisivaram]

@baluchicken Thank you for the PR. There was a failure with the same symptoms with this PR (https://builds.apache.org/job/kafka-pr-jdk8-scala2.11/3547/testReport/kafka.api/SaslGssapiSslEndToEndAuthorizationTest/testTwoConsumersWithDifferentSaslCredentials/). Unfortunately, only warning level logs are available, so the extra info level log didn't help. Can you see if you can catch the server startup exception and log the jaasContext that was written and then rethrow the exception? If you can't get to the jaasContext easily, you could just read the file based on the system property and display that (at error level in the catch block).

[rajinisivaram]

@baluchicken I have raised another PR to log the contents of the file when there is a failure.

[baluchicken]

Thanks, @rajinisivaram