support return AD job when get detector

src/main/java/com/amazon/opendistroforelasticsearch/ad/rest/handler/AnomalyDetectorFunction.java

@@ -20,6 +20,8 @@ public interface AnomalyDetectorFunction {
 
     /**
      * Performs this operation.
+     *
+     * Notes: don't forget to send back response via channel if you process response with this method.
      */
     void execute();
 }