change json log format

monitor.mjs

@@ -117,7 +117,7 @@ class Monitor {
                     //写入JSON格式的log
                     logFile = path.resolve(_self.systemLogDir) + '/json_stats.log';
                     let logData = {
-                        "time": currentTime,
+                        "timestamp": common.getTimestamp(),
                         "url": task.url,
                         "status": taskRes.task.status
                     };
@@ -131,7 +131,7 @@ class Monitor {
                     //写入JSON格式的log
                     logFile = path.resolve(_self.systemLogDir) + '/json_stats.log';
                     let logData = {
-                        "time": currentTime,
+                        "timestamp": common.getTimestamp(),
                         "url": task.url,
                         "status": task.status
                     };