Some tests intentionally cause the server to abort (e.g. fatal assertion). When quickly scanning the log output for a reason as to why the test failed, Server team engineers are misled by backtraces appearing in the output. We should write a message in MongoRunner.stopMongod() when the allowedExitCodes option is being used to test for an intentional abort.
Some tests intentionally cause the server to fassert. When diagnosing a test failure, people are sometimes thrown off by seeing fassert backtraces in the logs for fasserts that are expected. If we create a server option to suppress backtraces for fasserts with certain codes, then the test use this option to prevent expected fasserts from appearing in the logs.