kinesis.ShardReadersPoolTest.shouldStopReadersPoolAlsoWhenExceptionsOccurDuringStopping is flaky

shouldStopReadersPoolAlsoWhenExceptionsOccurDuringStopping fails due to incomplete interactions with the mock.

Wanted but not invoked: firstIterator.readNextBatch(); -> at org.apache.beam.sdk.io.kinesis.ShardReadersPoolTest.shouldStopReadersPoolAlsoWhenExceptionsOccurDuringStopping(ShardReadersPoolTest.java:244) However, there were other interactions with this mock: -> at org.apache.beam.sdk.io.kinesis.ShardReadersPoolTest.shouldStopReadersPoolAlsoWhenExceptionsOccurDuringStopping(ShardReadersPoolTest.java:241)

https://builds.apache.org/job/beam_PreCommit_Java_MavenInstall/org.apache.beam$beam-sdks-java-io-kinesis/17390/testReport/junit/org.apache.beam.sdk.io.kinesis/ShardReadersPoolTest/shouldStopReadersPoolAlsoWhenExceptionsOccurDuringStopping/