HDDS-9896. Fix for NullPointerException when replicating closed container using freon

[hemantk-12]

What changes were proposed in this pull request?

We are seeing NPE when replicating closed container using freon

java.lang.NullPointerException
 at org.apache.hadoop.ozone.container.replication.ContainerImporter.chooseNextVolume(ContainerImporter.java:146)
 at org.apache.hadoop.ozone.container.replication.DownloadAndImportReplicator.replicate(DownloadAndImportReplicator.java:77)
 at org.apache.hadoop.ozone.container.replication.ReplicationTask.runTask(ReplicationTask.java:122)
 at org.apache.hadoop.ozone.container.replication.ReplicationSupervisor$TaskRunner.run(ReplicationSupervisor.java:359)
 at org.apache.hadoop.ozone.freon.ClosedContainerReplicator.lambda$replicateContainer$1(ClosedContainerReplicator.java:224)
 at com.codahale.metrics.Timer.time(Timer.java:101)
 at org.apache.hadoop.ozone.freon.ClosedContainerReplicator.replicateContainer(ClosedContainerReplicator.java:221)
 at org.apache.hadoop.ozone.freon.BaseFreonGenerator.tryNextTask(BaseFreonGenerator.java:220)
 at org.apache.hadoop.ozone.freon.BaseFreonGenerator.taskLoop(BaseFreonGenerator.java:200)
 at org.apache.hadoop.ozone.freon.BaseFreonGenerator.lambda$startTaskRunners$0(BaseFreonGenerator.java:174)
 at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
 at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
 at java.base/java.lang.Thread.run(Thread.java:834)

This change is to fix NPE and pass non-null volumeSet when creating ContainerImporter object to replicate closed container using freon. Also added @NotNull annotation on ContainerImporter's constructor for developers.

What is the link to the Apache JIRA

https://issues.apache.org/jira/browse/HDDS-9896

How was this patch tested?

Existing unit and integ tests for now.

[kerneltime]

cc @DaveTeng0

[jojochuang]

LGTM.
But maybe we should have robot tests for freon commands in the future.