HDDS-5355. In ContainerStateMachine, share the executor threads between the containers.

[szetszwo]

What changes were proposed in this pull request?

//ContainerStateMachine
  private ExecutorService getCommandExecutor(
      ContainerCommandRequestProto requestProto) {
    int executorId = (int)(requestProto.getContainerID() % executors.length);
    return executors[executorId];
  }

In the code above, different containers having the same remainder (mod executors.length ) will use the same executor even if some other executors are idle.  Ideally, different containers should use a different executor if there are executors available.

What is the link to the Apache JIRA

https://issues.apache.org/jira/browse/HDDS-5355

How was this patch tested?

Existing unit tests.

[adoroszlai]

Thanks @szetszwo for the improvement.

[szetszwo]

Thanks @bshashikant for reviewing this and @adoroszlai for merging this!