fix(admin): 修复定时任务执行时间计算错误

- 修正了 JobScheduleHelper 类中的时间计算逻辑，使用 Long 类型替代 Integer 类型
- 避免了因数据类型溢出导致的时间计算错误
- 优化了 JobThread 类中的注释

xxl-job-admin/src/main/java/com/xxl/job/admin/core/thread/JobScheduleHelper.java

@@ -372,7 +372,7 @@ public class JobScheduleHelper {
             Date nextValidTime = new CronExpression(jobInfo.getScheduleConf()).getNextValidTimeAfter(fromTime);
             return nextValidTime;
         } else if (ScheduleTypeEnum.FIX_RATE == scheduleTypeEnum /*|| ScheduleTypeEnum.FIX_DELAY == scheduleTypeEnum*/) {
-            return new Date(fromTime.getTime() + Integer.valueOf(jobInfo.getScheduleConf())*1000 );
+            return new Date(fromTime.getTime() + Long.parseLong(jobInfo.getScheduleConf()) * 1000L);
         }
         return null;
     }

xxl-job-core/src/main/java/com/xxl/job/core/thread/JobThread.java

@@ -110,7 +110,7 @@ public class JobThread extends Thread{
 
             TriggerParam triggerParam = null;
             try {
-				// to check toStop signal, we need cycle, so wo cannot use queue.take(), instand of poll(timeout)
+				// to check toStop signal, we need cycle, so we cannot use queue.take(), instead of poll(timeout)
 				triggerParam = triggerQueue.poll(3L, TimeUnit.SECONDS);
 				if (triggerParam!=null) {
 					running = true;
@@ -206,7 +206,7 @@ public class JobThread extends Thread{
                 if(triggerParam != null) {
                     // callback handler info
                     if (!toStop) {
-                        // commonm
+                        // common
                         TriggerCallbackThread.pushCallBack(new HandleCallbackParam(
                         		triggerParam.getLogId(),
 								triggerParam.getLogDateTime(),