A common issue, especially when Hazelcast runs in Kubernetes pods with log4j2 logging,
is that shutdown logs are missing. The reason is that log4j2 registers its own shutdown
hook, alongside Hazelcast's own shutdown hook. Since the JVM does not guarantee
any ordering of shutdown hook execution, it can be the case that the log4j shutdown
hook shuts down loggers while Hazelcast is still performing shut down activities.
This results in missing important logs from the shutdown of Hazelcast members that
can be useful for troubleshooting.
This change introduces explicit shutdown of the log4j2 LogManager after Hazelcast Node
has been shut down: this does no harm when the log4j shutdown hook is enabled (as far as
I navigated the log4j code & tested the changes locally). When the shutdown hook is disabled,
it allows for clean logging of shutdown information.
Example of Hazelcast shutdown logging with GRACEFUL shutdown hook policy:
- without this change:
 ^C2023-11-20 16:26:02,988 [ INFO] [hz.ShutdownThread] [c.h.i.i.Node]: [127.0.0.1]:5701 [dev] [5.4.0-SNAPSHOT] Running shutdown hook... Current node state: ACTIVE
 - with this change:
 ^C2023-11-20 16:26:31,183 [ INFO] [hz.ShutdownThread] [c.h.i.i.Node]: [127.0.0.1]:5701 [dev] [5.4.0-SNAPSHOT] Running shutdown hook... Current node state: ACTIVE
 2023-11-20 16:26:31,185 [ INFO] [hz.ShutdownThread] [c.h.c.LifecycleService]: [127.0.0.1]:5701 [dev] [5.4.0-SNAPSHOT] [127.0.0.1]:5701 is SHUTTING_DOWN
 2023-11-20 16:26:31,191 [ INFO] [hz.ShutdownThread] [c.h.i.i.Node]: [127.0.0.1]:5701 [dev] [5.4.0-SNAPSHOT] Shutting down connection manager...
 2023-11-20 16:26:31,195 [ INFO] [hz.ShutdownThread] [c.h.i.i.Node]: [127.0.0.1]:5701 [dev] [5.4.0-SNAPSHOT] Shutting down node engine...
 2023-11-20 16:26:31,205 [ INFO] [hz.ShutdownThread] [c.h.i.i.NodeExtension]: [127.0.0.1]:5701 [dev] [5.4.0-SNAPSHOT] Destroying node NodeExtension.
 2023-11-20 16:26:31,206 [ INFO] [hz.ShutdownThread] [c.h.i.i.Node]: [127.0.0.1]:5701 [dev] [5.4.0-SNAPSHOT] Hazelcast Shutdown is completed in 18 ms.

Default is false, so Hazelcast will not explicitly shut down the logging
framework during graceful shutdown. When true, Hazelcast will
shutdown the backing logging framework as part of its graceful
shutdown procedure.