Broker should not set leader epoch if the list-offset request version < 4

The list-offset response added a new field in version 4:

        { "name": "LeaderEpoch", "type": "int32", "versions": "4+" }

And the compiled code would throw UnsupportedVersionException if that field is not default (-1) with version < 4. However, on the broker side we forget to add the logic to not setting this field based on the request version. This would cause old versioned clients' list-offset call to always get UnsupportedVersionException and an empty result would be returned.