Flaky test: TestSparkClient.testJobSubmission (still flaky)

 // Link the RPC and the promise so that events from one are propagated to the other as
      // needed.
      rpc.addListener(new GenericFutureListener<io.netty.util.concurrent.Future<Void>>() {
        @Override
        public void operationComplete(io.netty.util.concurrent.Future<Void> f) {
          if (f.isSuccess()) {
            handle.changeState(JobHandle.State.QUEUED);
          } else if (!promise.isDone()) {
            promise.setFailure(f.cause());
          }
        }
      });
      promise.addListener(new GenericFutureListener<Promise<T>>() {
        @Override
        public void operationComplete(Promise<T> p) {
          if (jobId != null) {
            jobs.remove(jobId);
          }
          if (p.isCancelled() && !rpc.isDone()) {
            rpc.cancel(true);
          }
        }
      });