增强监控

git-svn-id: http://code.alibabatech.com/svn/druid/trunk@345 b9813039-fb51-4c41-a8b9-e21c2acb5095

src/main/java/com/alibaba/druid/pool/PoolableConnection.java

@@ -123,6 +123,7 @@ public class PoolableConnection implements PooledConnection, Connection {
             listener.connectionClosed(new ConnectionEvent(this));
         }
 
+        holder.reset();
         holder.getDataSource().recycle(this);
         holder = null;
         conn = null;