GremlinExecutor: Timeout future not cancelled on successful script evaluation

This bug seems to be introduced by TINKERPOP-1714. The timeout future in GremlinExecutor.eval() is not cancelled when the evaluation future is completed successfully before the timeout (lines 304ff). This was done correctly before the changes introduced by TINKERPOP-1714. Code to reproduce:

try (GremlinExecutor executor = GremlinExecutor.build().scriptEvaluationTimeout(15_000).create()) {
  executor.eval("1+1").get();
} catch (Exception e) {
  // NOOP
}

When the code leaves the try-block it calls GremlinExecutor.close() which will clean up executorService and scheduledExecutorService, but because the timeout future is not cancelled this will hang until the future is finished (here 15s).

Workaround: Provide an own ExecutorService when constructing a GremlinExecutor instance and cancel all tasks when the script evaluation is finished successfully.