"Scheduler already terminated" occurs when RemoteInterpreter.close() doesn't succeed

If there're some issue for remote interpreter to not respond properly (e.g. OOME), restarting interpreter shutdowns remote scheduler but doesn't shutdown remote interpreter process because reference count doesn't reach 0.

You can refer summarized logs from here - https://gist.github.com/HeartSaVioR/26190a71df6815aa62b8.