This change fixes the driver tests "VMServiceFlutterDriver with logCommunicationToFile logCommunicationToFile logCommunicationToFile = false" and "WebFlutterDriver with logCommunicationToFile logCommunicationToFile = false" so that they will no longer fail when run locally.

The issue was one of not cleaning up the log files after the test ran, so a later run with the same name would see it. Presumably on the servers the tests are run in a different environment where the names or locations of the output files end up being different.