@Sajesh PP - You will get below messages in the logs during the time of shutdown.
2019-03-14 17:10:57,270 INFO impl.MetricsSystemImpl (MetricsSystemImpl.java:shutdown(606)) - NodeManager metrics system shutdown complete.
2019-03-14 17:10:57,274 INFO nodemanager.NodeManager (LogAdapter.java:info(45)) - SHUTDOWN_MSG:
/************************************************************
SHUTDOWN_MSG: Shutting down NodeManager at abc.example.com/xxx.xx.xx.xxx
************************************************************
You need to grep in the same in the NM logs. If you are not finding anything, then you need to check other files created in the NM logs directory.