ITClosedSessionTest.testReadWriteTransactionNoRecreation is flaky

[olavloite]

https://source.cloud.google.com/results/invocations/1e8310da-7ac3-4523-b421-0b7c1d65b74d/targets/cloud-devrel%2Fclient-libraries%2Fjava%2Fjava-spanner%2Fpresubmit%2Fintegration/log

Cloud Spanner sometimes returns Session was deleted during operation runtime. instead of Session not found.