HADOOP-17511. Auditing, stabilization

* Select is spanned properly
* HttpReferrer adds dynamic eval of current thread.
* Every entry point in S3A code which creates a span is tagged
  @AuditSpan.AuditEntryPoint. This is to hint what is/isn't spanned.

Public code MUST go through an AuditEntryPoint; internal code
within an existing span MUST NOT -doing so will lose the first
span.

+revert test fix of ITestAssumeRole as it is covered in HADOOP-17476/apache#2777

Change-Id: I2cfdba907df0dcc76629e5af8effeed8d25d5933

Author: steveloughran

hadoop-tools/hadoop-aws/src/main/java/org/apache/hadoop/fs/s3a/MultipartUtils.java

@@ -177,7 +177,7 @@ public String toString() {
 
     @Retries.RetryTranslated
     private void requestNextBatch() throws IOException {
-      try (final AuditSpan span = auditSpan.activate()) {
+      try (AuditSpan span = auditSpan.activate()) {
         ListMultipartUploadsRequest req = requestFactory
             .newListMultipartUploadsRequest(prefix);
         if (!firstListing) {