Enable ealy stopped trials data for tuners.

[scarlett2018]

If a trial is early stopped, no metric data is sent to tuner. Some users also want tuner to know the metric data of those early stopped trials.

1. NNImanager find the last metric data when a trial is killed, and send this metric data to tuner. Let webui show the last intermediate result as final result.
2. Two ways:
   • Advisor with functionalities of tuner and assessor;
   • Also send early stop final state with final intermediate data to tuner.
3. Tuner tolerates the duplicate messages of early stop.