GUACAMOLE-364: address style consistency issues

guacamole-ext/src/main/java/org/apache/guacamole/net/event/listener/AuthenticationFailureListener.java

@@ -28,6 +28,7 @@ import org.apache.guacamole.net.event.AuthenticationFailureEvent;
  * be used to cancel the authentication failure.
  */
 public interface AuthenticationFailureListener extends Listener {
+
     /**
      * Event hook which fires immediately after a user's authentication attempt
      * fails.

guacamole-ext/src/main/java/org/apache/guacamole/net/event/listener/Listener.java

@@ -15,7 +15,6 @@
  *  KIND, either express or implied.  See the License for the
  *  specific language governing permissions and limitations
  *  under the License.
- *
  */
 
 package org.apache.guacamole.net.event.listener;