Log listener Throwables in default promise

Motivation:

The logging statements in i.n.u.c.DefaultPromise do not emit the
caught Throwable when a Throwable is thrown while a listener is being
notified of completed or progressed operations.

Modifications:

This issue arises because the logging message has a single placeholder
but is passing two additional arguments, the second one being the
caught Throwable that is thus quietly not logged. We address this by
modifying the logging statements to ensure the caught Throwable is
logged. In this case, the preferred approach is to use the logger
override that accepts a message and a Throwable parameter since logger
implementations might have special handling for this case.

Result:

Log messages from i.n.u.c.DefaultPromise when a Throwable is thrown
while notifying a listener of completed or progressed operations will
contain the caught Throwable.

common/src/main/java/io/netty/util/concurrent/DefaultPromise.java

@@ -520,7 +520,7 @@ public class DefaultPromise<V> extends AbstractFuture<V> implements Promise<V> {
         try {
             l.operationComplete(future);
         } catch (Throwable t) {
-            logger.warn("An exception was thrown by {}.operationComplete()", l.getClass().getName(), t);
+            logger.warn("An exception was thrown by " + l.getClass().getName() + ".operationComplete()", t);
         }
     }
 
@@ -747,7 +747,7 @@ public class DefaultPromise<V> extends AbstractFuture<V> implements Promise<V> {
         try {
             l.operationProgressed(future, progress, total);
         } catch (Throwable t) {
-            logger.warn("An exception was thrown by {}.operationProgressed()", l.getClass().getName(), t);
+            logger.warn("An exception was thrown by " + l.getClass().getName() + ".operationProgressed()", t);
         }
     }