refactor the log

src/main/java/org/bench4q/agent/scenario/ScenarioEngine.java

@@ -97,7 +97,7 @@ public class ScenarioEngine {
 					executorService.execute(new Runnable() {
 						public void run() {
 							doRunScenario(scenarioContext);
-							System.out.println("end for once");
+							logger.info("end for once!");
 						}
 					});
 				}