HADOOP-16340. ABFS driver continues to retry on IOException responses from REST operations.

Contributed by Robert Levas.

This makes the HttpException constructor protected rather than public, so it is possible
to implement custom subclasses of this exception -exceptions which will not be retried.

Change-Id: Ie8aaa23a707233c2db35948784908b6778ff3a8f

hadoop-tools/hadoop-azure/src/main/java/org/apache/hadoop/fs/azurebfs/oauth2/AzureADAuthenticator.java

@@ -165,6 +165,8 @@ public final class AzureADAuthenticator {
    * requestId and error message, it is thrown when AzureADAuthenticator
    * failed to get the Azure Active Directory token.
    */
+  @InterfaceAudience.LimitedPrivate("authorization-subsystems")
+  @InterfaceStability.Unstable
   public static class HttpException extends IOException {
     private final int httpErrorCode;
     private final String requestId;
@@ -191,7 +193,7 @@ public final class AzureADAuthenticator {
       return this.requestId;
     }
 
-    HttpException(
+    protected HttpException(
         final int httpErrorCode,
         final String requestId,
         final String message,