HDDS-7806. Add unit tests for push replication

[adoroszlai]

What changes were proposed in this pull request?

Add unit test for SendContainerOutputStream and PushReplicator.

https://issues.apache.org/jira/browse/HDDS-7806

How was this patch tested?

[INFO] Running org.apache.hadoop.ozone.container.replication.TestSendContainerOutputStream
[INFO] Tests run: 8, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 1.324 s - in org.apache.hadoop.ozone.container.replication.TestSendContainerOutputStream
[INFO] Running org.apache.hadoop.ozone.container.replication.TestPushReplicator
[INFO] Tests run: 3, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 1.346 s - in org.apache.hadoop.ozone.container.replication.TestPushReplicator

[sodonnel]

LGTM

[adoroszlai]

Thanks @sodonnel for the review.

[kaijchen]

Hi @adoroszlai, looks like TestPushReplicator is flaky.

[adoroszlai]

Thanks @kaijchen, I also encountered this in followup changes. I'll disable it until I can fix it.