Make sure all partitions have been closed in broker shutdown

[mooc9988]

When a broker is shutting down, a partition may be closed due to

• leader change
• or log manager's closure.

For the former case, the broker need to wait for partition's closure.

[mooc9988]

When a broker is shutting down, all partitions will be reassigned to other active brokers. It will lead to partitions' closure in the shutting down broker. Partition's closure will then remove the log from LogManager. For now, partition's closure is done in partitionOpenCloseExecutors. Therefore, broker have to wait for partitionOpenCloseExecutors shutting down.

If the broker is the last broker, partitions in this broker will turn into followers. They will all be closed in LogManager's shutting down.