add exection sorter test

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

@@ -21,16 +21,8 @@ public class DataSourceClosedException extends SQLException {
 
     private static final long serialVersionUID = 1L;
 
-    public DataSourceClosedException(){
-        super();
-    }
-
     public DataSourceClosedException(String reason){
         super(reason);
     }
 
-    public DataSourceClosedException(Throwable cause){
-        super(cause);
-    }
-
 }