IT Failure(google-cloud-trace): getTraceTest

Flaky error during nightly build ([rerun](http://sponge/ff0f5761-f131-4a97-a6dd-b49e07c1dc47)):

```
15:45:53:107 [INFO] Running com.google.cloud.trace.v1.TraceServiceClientTest
15:45:53:458 [INFO] Tests run: 6, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.348 s - in com.google.cloud.trace.v1.TraceServiceClientTest
15:45:53:459 [INFO] Running com.google.cloud.trace.v1.it.ITSystemTest
15:46:05:178 [ERROR] Tests run: 2, Failures: 0, Errors: 1, Skipped: 0, Time elapsed: 11.707 s <<< FAILURE! - in com.google.cloud.trace.v1.it.ITSystemTest
15:46:05:180 [ERROR] com.google.cloud.trace.v1.it.ITSystemTest.getTraceTest Time elapsed: 5.204 s <<< ERROR!
com.google.api.gax.rpc.NotFoundException: io.grpc.StatusRuntimeException: NOT_FOUND: Requested entity was not found.
at com.google.api.gax.rpc.ApiExceptionFactory.createException(ApiExceptionFactory.java:90)
at com.google.api.gax.rpc.ApiExceptionFactory.createException(ApiExceptionFactory.java:41)
at com.google.api.gax.grpc.GrpcApiExceptionFactory.create(GrpcApiExceptionFactory.java:86)
at com.google.api.gax.grpc.GrpcApiExceptionFactory.create(GrpcApiExceptionFactory.java:66)
at com.google.api.gax.grpc.GrpcExceptionCallable$ExceptionTransformingFuture.onFailure(GrpcExceptionCallable.java:97)
at com.google.api.core.ApiFutures$1.onFailure(ApiFutures.java:84)
at com.google.common.util.concurrent.Futures$CallbackListener.run(Futures.java:1132)
at com.google.common.util.concurrent.DirectExecutor.execute(DirectExecutor.java:31)
at com.google.common.util.concurrent.AbstractFuture.executeListener(AbstractFuture.java:1270)
at com.google.common.util.concurrent.AbstractFuture.complete(AbstractFuture.java:1038)
at com.google.common.util.concurrent.AbstractFuture.setException(AbstractFuture.java:808)
at io.grpc.stub.ClientCalls$GrpcFuture.setException(ClientCalls.java:574)
at io.grpc.stub.ClientCalls$UnaryStreamToFuture.onClose(ClientCalls.java:544)
at io.grpc.PartialForwardingClientCallListener.onClose(PartialForwardingClientCallListener.java:39)
at io.grpc.ForwardingClientCallListener.onClose(ForwardingClientCallListener.java:23)
at io.grpc.ForwardingClientCallListener$SimpleForwardingClientCallListener.onClose(ForwardingClientCallListener.java:40)
at com.google.api.gax.grpc.ChannelPool$ReleasingClientCall$1.onClose(ChannelPool.java:541)
at io.grpc.internal.ClientCallImpl.closeObserver(ClientCallImpl.java:567)
at io.grpc.internal.ClientCallImpl.access$300(ClientCallImpl.java:71)
at io.grpc.internal.ClientCallImpl$ClientStreamListenerImpl$1StreamClosed.runInternal(ClientCallImpl.java:735)
at io.grpc.internal.ClientCallImpl$ClientStreamListenerImpl$1StreamClosed.runInContext(ClientCallImpl.java:716)
at io.grpc.internal.ContextRunnable.run(ContextRunnable.java:37)
at io.grpc.internal.SerializingExecutor.run(SerializingExecutor.java:133)
at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1136)
at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:635)
at java.base/java.lang.Thread.run(Thread.java:833)
Suppressed: com.google.api.gax.rpc.AsyncTaskException: Asynchronous task failed
at com.google.api.gax.rpc.ApiExceptions.callAndTranslateApiException(ApiExceptions.java:57)
at com.google.api.gax.rpc.UnaryCallable.call(UnaryCallable.java:112)
at com.google.cloud.trace.v1.TraceServiceClient.getTrace(TraceServiceClient.java:379)
at com.google.cloud.trace.v1.it.ITSystemTest.getTraceTest(ITSystemTest.java:87)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:568)
at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:59)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:56)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
at org.junit.runners.ParentRunner$3.evaluate(ParentRunner.java:306)
at org.junit.runners.BlockJUnit4ClassRunner$1.evaluate(BlockJUnit4ClassRunner.java:100)
at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:366)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:103)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:63)
at org.junit.runners.ParentRunner$4.run(ParentRunner.java:331)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:79)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:329)
at org.junit.runners.ParentRunner.access$100(ParentRunner.java:66)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:293)
at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:26)
at org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:27)
at org.junit.runners.ParentRunner$3.evaluate(ParentRunner.java:306)
at org.junit.runners.ParentRunner.run(ParentRunner.java:413)
at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
at org.junit.runner.JUnitCore.run(JUnitCore.java:115)
at org.junit.vintage.engine.execution.RunnerExecutor.execute(RunnerExecutor.java:42)
at org.junit.vintage.engine.VintageTestEngine.executeAllChildren(VintageTestEngine.java:80)
at org.junit.vintage.engine.VintageTestEngine.execute(VintageTestEngine.java:72)
at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:147)
at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:127)
at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:90)
at org.junit.platform.launcher.core.EngineExecutionOrchestrator.lambda$execute$0(EngineExecutionOrchestrator.java:55)
at org.junit.platform.launcher.core.EngineExecutionOrchestrator.withInterceptedStreams(EngineExecutionOrchestrator.java:102)
at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:54)
at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:114)
at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:86)
at org.junit.platform.launcher.core.DefaultLauncherSession$DelegatingLauncher.execute(DefaultLauncherSession.java:86)
at org.apache.maven.surefire.junitplatform.LazyLauncher.execute(LazyLauncher.java:50)
at org.apache.maven.surefire.junitplatform.JUnitPlatformProvider.execute(JUnitPlatformProvider.java:184)
at org.apache.maven.surefire.junitplatform.JUnitPlatformProvider.invokeAllTests(JUnitPlatformProvider.java:148)
at org.apache.maven.surefire.junitplatform.JUnitPlatformProvider.invoke(JUnitPlatformProvider.java:122)
at org.apache.maven.surefire.booter.ForkedBooter.runSuitesInProcess(ForkedBooter.java:385)
at org.apache.maven.surefire.booter.ForkedBooter.execute(ForkedBooter.java:162)
at org.apache.maven.surefire.booter.ForkedBooter.run(ForkedBooter.java:507)
at org.apache.maven.surefire.booter.ForkedBooter.main(ForkedBooter.java:495)
Caused by: io.grpc.StatusRuntimeException: NOT_FOUND: Requested entity was not found.
at io.grpc.Status.asRuntimeException(Status.java:539)
... 14 more

15:46:05:200 [INFO] Running com.google.cloud.trace.v2.TraceServiceClientTest
15:46:05:269 [INFO] Tests run: 6, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.09 s - in com.google.cloud.trace.v2.TraceServiceClientTest
15:46:05:269 [INFO] Running com.google.cloud.trace.v2.it.ITSystemTest
15:46:05:621 [INFO] Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.359 s - in com.google.cloud.trace.v2.it.ITSystemTest
15:46:05:967 [INFO]
15:46:05:968 [INFO] Results:
15:46:05:968 [INFO]
15:46:05:968 [ERROR] Errors:
15:46:05:968 [ERROR] ITSystemTest.getTraceTest » NotFound io.grpc.StatusRuntimeException: NOT_FOUND: Requested entity was not found.
```