HDDS-9659. Intermittent failure in TestOzoneECClient#testPartialStripeWithPartialChunkRetry

[adoroszlai]

What changes were proposed in this pull request?

Fix intermittent failures in testPartialStripeWithPartialChunkRetry:

IndexOutOfBoundsException: Index: -1
	at java.util.Collections$EmptyList.get(Collections.java:4456)
	at java.util.Collections$UnmodifiableList.get(Collections.java:1311)
	at org.apache.hadoop.ozone.client.io.ECBlockOutputStreamEntry.calculateChecksum(ECBlockOutputStreamEntry.java:416)
	at org.apache.hadoop.ozone.client.io.ECKeyOutputStream.commitStripeWrite(ECKeyOutputStream.java:266)
	at org.apache.hadoop.ozone.client.io.ECKeyOutputStream.flushStripeToDatanodes(ECKeyOutputStream.java:585)
	at org.apache.hadoop.ozone.client.io.ECKeyOutputStream.flushStripeFromQueue(ECKeyOutputStream.java:567)

and

NullPointerException
	at org.apache.hadoop.ozone.client.io.ECBlockOutputStreamEntry.calculateChecksum(ECBlockOutputStreamEntry.java:412)
	at org.apache.hadoop.ozone.client.io.ECKeyOutputStream.commitStripeWrite(ECKeyOutputStream.java:266)
	at org.apache.hadoop.ozone.client.io.ECKeyOutputStream.flushStripeToDatanodes(ECKeyOutputStream.java:585)
	at org.apache.hadoop.ozone.client.io.ECKeyOutputStream.flushStripeFromQueue(ECKeyOutputStream.java:567)

and

ConcurrentModificationException
	at java.util.HashMap$HashIterator.remove(HashMap.java:1483)
	at org.apache.hadoop.ozone.client.MockXceiverClientFactory.mockStorageFailure(MockXceiverClientFactory.java:71)
	at org.apache.hadoop.ozone.client.MockXceiverClientFactory.mockStorageFailure(MockXceiverClientFactory.java:57)
	at org.apache.hadoop.ozone.client.MockXceiverClientFactory.setFailedStorages(MockXceiverClientFactory.java:47)
	at org.apache.hadoop.ozone.client.TestOzoneECClient.testPartialStripeWithPartialChunkRetry(TestOzoneECClient.java:1037)

1. Completely initialize array of ECBlockOutputStream before exposing it via blockOutputStream member variable.
2. Fix ConcurrentModificationException in MockXceiverClientFactory by changing to concurrent set/map.

https://issues.apache.org/jira/browse/HDDS-9659

How was this patch tested?

Passed 100x:
https://github.com/adoroszlai/ozone/actions/runs/6862777705

and 250x:
https://github.com/adoroszlai/ozone/actions/runs/6863403759

For reference, failed 2/100 without the fix:
https://github.com/adoroszlai/ozone/actions/runs/6873776049/job/18695127972

[aswinshakil]

Thanks for the patch @adoroszlai. LGTM

[adoroszlai]

Thanks @aswinshakil for the review.