See HADOOP-18091. S3A auditing leaks memory through ThreadLocal references
* Adds a new option fs.s3a.audit.enabled to controls whether or not auditing
is enabled. This is false by default.
* When false, the S3A auditing manager is NoopAuditManagerS3A,
which was formerly only used for unit tests and
during filsystem initialization.
* When true, ActiveAuditManagerS3A is used for managing auditing,
allowing auditing events to be reported.
* updates documentation and tests.
This patch does not fix the underlying leak. When auditing is enabled,
long-lived threads will retain references to the audit managers
of S3A filesystem instances which have already been closed.
Contributed by Steve Loughran.
b795f6f9a8