执行器log4j配置优化，去除无效属性；from：zhugw@github

xxl-job-executor-example/src/main/resources/log4j.xml

@@ -27,6 +27,7 @@
         </layout>
     </appender>
 
+
     <logger name="com.xxl.job.core" additivity="false">
     	<level value="INFO" />
         <appender-ref ref="CONSOLE" />