Bug/last will delivery

[dmytro-landiak]

Pull Request description

During the TBMQ shutdown, this issue may occur when last will messages are attempted to be delivered, but the scheduler has already been stopped. Resulting in:

java.util.concurrent.RejectedExecutionException: Task 
java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask@4c7825d8
[Not completed, task = java.util.concurrent.Executors$RunnableAdapter@25380416
[Wrapped task = org.thingsboard.mqtt.broker.service.mqtt.will.DefaultLastWillService$$Lambda$3299/0x00007fc82926e418@7b067819]]
rejected from java.util.concurrent.ScheduledThreadPoolExecutor@47e838a3
[Terminated, pool size = 0, active threads = 0, queued tasks = 0, completed tasks = 16]

    at java.base/java.util.concurrent.ThreadPoolExecutor$AbortPolicy.rejectedExecution(ThreadPoolExecutor.java:2065)
    at java.base/java.util.concurrent.ThreadPoolExecutor.reject(ThreadPoolExecutor.java:833)
    at java.base/java.util.concurrent.ScheduledThreadPoolExecutor.delayedExecute(ScheduledThreadPoolExecutor.java:340)
    at java.base/java.util.concurrent.ScheduledThreadPoolExecutor.schedule(ScheduledThreadPoolExecutor.java:562)
    at java.base/java.util.concurrent.Executors$DelegatedScheduledExecutorService.schedule(Executors.java:813)
    at org.thingsboard.mqtt.broker.service.mqtt.will.DefaultLastWillService.scheduleLastWill(DefaultLastWillService.java:121)
    at org.thingsboard.mqtt.broker.service.mqtt.will.DefaultLastWillService.removeAndExecuteLastWillIfNeeded(DefaultLastWillService.java:108)
    at org.thingsboard.mqtt.broker.actors.client.service.disconnect.DisconnectServiceImpl.clearClientSession(DisconnectServiceImpl.java:163)
    at org.thingsboard.mqtt.broker.actors.client.service.disconnect.DisconnectServiceImpl.disconnect(DisconnectServiceImpl.java:91)
    at org.thingsboard.mqtt.broker.actors.client.service.ActorProcessorImpl.disconnect(ActorProcessorImpl.java:336)
    at org.thingsboard.mqtt.broker.actors.client.service.ActorProcessorImpl.onDisconnect(ActorProcessorImpl.java:331)
    at org.thingsboard.mqtt.broker.actors.client.ClientActor.doProcess(ClientActor.java:129)
    at org.thingsboard.mqtt.broker.actors.service.ContextAwareActor.process(ContextAwareActor.java:44)
    at org.thingsboard.mqtt.broker.actors.TbActorMailbox.processMailbox(TbActorMailbox.java:145)
    at java.base/java.util.concurrent.ForkJoinTask$RunnableExecuteAction.exec(ForkJoinTask.java:1395)
    at java.base/java.util.concurrent.ForkJoinTask.doExec(ForkJoinTask.java:373)
    at java.base/java.util.concurrent.ForkJoinPool$WorkQueue.topLevelExec(ForkJoinPool.java:1182)
    at java.base/java.util.concurrent.ForkJoinPool.scan(ForkJoinPool.java:1655)
    at java.base/java.util.concurrent.ForkJoinPool.runWorker(ForkJoinPool.java:1622)
    at java.base/java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:165)

General checklist

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• [x] Labels that classify your pull request have been added.
• [x] The milestone is specified and corresponds to fix version.
• [x] Description references specific issue.
• [x] Description contains human-readable scope of changes.
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• [x] No merge conflicts, commented blocks of code, code formatting issues.
• [x] Changes are backward compatible or upgrade script is provided.

Front-End feature checklist

• [x] Screenshots with affected component(s) are added. The best option is to provide 2 screens: before and after changes;
• [x] If you change the widget or other API, ensure it is backward-compatible or upgrade script is present.

Back-End feature checklist

• [x] Added corresponding unit and/or integration test(s). Provide written explanation in the PR description if you have failed to add tests.
• [x] If new dependency was added: the dependency tree is checked for conflicts.