【bug】当Sermant长时间无法和backend-lite建立连接，心跳服务将无法再上报心跳

[luanwenfei-venus]

What happened?

开启心跳后，如果长时间没有连接上后端，将无法上报心跳，并抛出如下的异常 Exception in thread "Thread-1" java.util.concurrent.RejectedExecutionException: Task com.huaweicloud.sermant.implement.service.send.NettyClient$$Lambda$24/1083915630@6d2252b0 rejected from java.util.concurrent.ThreadPoolExecutor@3ed4f214[Running, pool size = 10, active threads = 10, queued tasks = 1000, completed tasks = 1313] at java.util.concurrent.ThreadPoolExecutor$AbortPolicy.rejectedExecution(ThreadPoolExecutor.java:2063) at java.util.concurrent.ThreadPoolExecutor.reject(ThreadPoolExecutor.java:830) at java.util.concurrent.ThreadPoolExecutor.execute(ThreadPoolExecutor.java:1379) at com.huaweicloud.sermant.implement.service.send.NettyClient.sendData(NettyClient.java:174) at com.huaweicloud.sermant.implement.service.heartbeat.HeartbeatServiceImpl.execute(HeartbeatServiceImpl.java:127) at com.huaweicloud.sermant.implement.service.heartbeat.HeartbeatServiceImpl.access$000(HeartbeatServiceImpl.java:53) at com.huaweicloud.sermant.implement.service.heartbeat.HeartbeatServiceImpl$1.run(HeartbeatServiceImpl.java:87) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) at java.lang.Thread.run(Thread.java:750)

How can we reproduce it (as minimally and precisely as possible)?

可以将启动sermant并且开启心跳服务，将心跳上报时间改为1000ms，断开十分钟左右，将重现此问题

Anything else we need to know?

No response

Sermant version

0.7.0

OS version

```console # On Linux: $ cat /etc/os-release # paste output here $ uname -a # paste output here # On Windows: C:\> wmic os get Caption, Version, BuildNumber, OSArchitecture # paste output here ```

[github-actions[bot]]

This issue seems to be Stale. We will close it in a few days.

[github-actions[bot]]

We close this issue because it hasn't been updated in a while. Remove Stale label if you want to reopen it.