Intermittent failure in RemoteProxyControllerProtocolTestCase.testClosesBeforePrepare()

I can't get it to fail any more, but I swear it was!

At line 496

Assert.assertEquals(1, commitControl.txCompletionStatus.get());

commitControl.txCompletionStatus.get() was returning -1.

Which would indicate operationFailed() was not called.

I see this when testing the AS7-2702 fix. I can't see how that patch would affect the timing of calls to operationFailed, so I'm committing the patch.