s2a: FakeS2AServerTest is flaky

[ejona86]

https://github.com/grpc/grpc-java/actions/runs/19276006644/job/55115854477?pr=12468 (logs)

I think RPCs are starting after the s2a channel is shut down. This might have started with #12424. Note that #12489 was not merged when this test failed.

FakeS2AServerTest > callS2AServerOnce_getTlsConfiguration_returnsValidResult FAILED
    java.util.concurrent.ExecutionException: io.grpc.StatusRuntimeException: UNAVAILABLE: Channel shutdown invoked
        at com.google.common.util.concurrent.AbstractFuture.getDoneValue(AbstractFuture.java:292)
        at com.google.common.util.concurrent.AbstractFutureState.blockingGet(AbstractFutureState.java:235)
        at com.google.common.util.concurrent.Platform.get(Platform.java:54)
        at com.google.common.util.concurrent.AbstractFuture.get(AbstractFuture.java:253)
        at com.google.common.util.concurrent.AbstractFuture$TrustedFuture.get(AbstractFuture.java:96)
        at io.grpc.s2a.internal.handshaker.FakeS2AServerTest.callS2AServerOnce_getTlsConfiguration_returnsValidResult(FakeS2AServerTest.java:163)

        Caused by:
        io.grpc.StatusRuntimeException: UNAVAILABLE: Channel shutdown invoked
            at app//io.grpc.Status.asRuntimeException(Status.java:532)
            at app//io.grpc.stub.ClientCalls$StreamObserverToCallListenerAdapter.onClose(ClientCalls.java:581)
            at app//io.grpc.internal.DelayedClientCall$DelayedListener$3.run(DelayedClientCall.java:487)
            at app//io.grpc.internal.DelayedClientCall$DelayedListener.drainPendingCallbacks(DelayedClientCall.java:526)
            at app//io.grpc.internal.DelayedClientCall$1DrainListenerRunnable.runInContext(DelayedClientCall.java:315)
            at app//io.grpc.internal.ContextRunnable.run(ContextRunnable.java:37)
            at java.base@21.0.9/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1144)
            at java.base@21.0.9/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:642)
            at java.base@21.0.9/java.lang.Thread.run(Thread.java:1583)

@rmehta19

[rmehta19]

Thanks for letting me know about this Eric, I'll take a look at this and send out a fix as needed

[ejona86]

Looks like it is unrelated to #12424. I was able to reproduce inside Google with --runs_per_test; it fails 1-3 out of 1000 times