What changes were proposed in this pull request?

testContainerExclusionWithClosedContainerException intermittently fails at the datanode assertion (Expecting empty but was: [<uuid>(null/null)]).

The test asserts that after a ClosedContainerException only the closed container is excluded. But under the default ALL_COMMITTED watch level, a momentarily-slow follower whose watch-for-commit times out is recorded in the client exclude list — intended slow-node-avoidance behaviour of the configurable watchType (HDDS-2887). So an empty datanode set is not an invariant under ALL_COMMITTED; the assertion predates the watchType config and never accounted for it.

The test's subject is container exclusion, which is independent of the watch level. This removes the non-invariant getDatanodes().isEmpty() assertion (the container and pipeline assertions stay); watch-level datanode exclusion is already covered by testDatanodeExclusionWithMajorityCommit.

What is the link to the Apache JIRA

https://issues.apache.org/jira/browse/HDDS-15605

How was this patch tested?

intermittent-test-check on the fork, TestFailureHandlingByClient, test-name=ALL, 100 runs each (10 splits x 10 iterations):

• This branch: the assertion did not recur (0/100). (run)
• master baseline, same harness: the assertion reproduced in ~5/100 runs (Expecting empty but was: [...]), matching the reported intermittency. (run)
• Remaining noise, unrelated to this change (present on master too):
  • A TimeoutException in TestHelper.waitForContainerClose (container state transition not completing under the harness's extreme parallel load of 10 concurrent splits); it occurs before the modified assertion and is a pre-existing load-sensitivity of the test.
  • testDatanodeExclusionWithMajorityCommit failures are the known HDDS-13972 (@Flaky).