ATLAS-2958: updated hooks to log exceptions on all notification failures

notification/src/main/java/org/apache/atlas/hook/AtlasHook.java

@@ -173,7 +173,6 @@ public abstract class AtlasHook {
         }
 
         final int maxAttempts         = maxRetries < 1 ? 1 : maxRetries;
-        final String message             = messages.toString();
         Exception notificationFailure = null;
 
         for (int numAttempt = 1; numAttempt <= maxAttempts; numAttempt++) {
@@ -214,14 +213,16 @@ public abstract class AtlasHook {
             }
         }
 
+        if (notificationFailure != null) {
             if (shouldLogFailedMessages && notificationFailure instanceof NotificationException) {
                 final List<String> failedMessages = ((NotificationException) notificationFailure).getFailedMessages();
 
                 for (String msg : failedMessages) {
                     logger.log(msg);
                 }
+            }
 
-            LOG.error("Giving up after {} failed attempts to send notification to Atlas: {}", maxAttempts, message, notificationFailure);
+            LOG.error("Giving up after {} failed attempts to send notification to Atlas: {}", maxAttempts, messages.toString(), notificationFailure);
         }
     }