MINOR: Add log when the consumer does not send an offset commit due to not being part of an active group (#6404)

Reviewers: Jason Gustafson <jason@confluent.io>

clients/src/main/java/org/apache/kafka/clients/consumer/internals/ConsumerCoordinator.java

@@ -810,15 +810,16 @@ public final class ConsumerCoordinator extends AbstractCoordinator {
         }
 
         final Generation generation;
-        if (subscriptions.partitionsAutoAssigned())
+        if (subscriptions.partitionsAutoAssigned()) {
             generation = generation();
-        else
-            generation = Generation.NO_GENERATION;
-
             // if the generation is null, we are not part of an active group (and we expect to be).
             // the only thing we can do is fail the commit and let the user rejoin the group in poll()
-        if (generation == null)
+            if (generation == null) {
+                log.info("Failing OffsetCommit request since the consumer is not part of an active group");
                 return RequestFuture.failure(new CommitFailedException());
+            }
+        } else
+            generation = Generation.NO_GENERATION;
 
         OffsetCommitRequest.Builder builder = new OffsetCommitRequest.Builder(
                 new OffsetCommitRequestData()