DefaultStrategy only receives successful training replies

[srcansiz]

The default behavior of the default strategy is that if any nodes returns an unsuccessful reply the training round should fail. However, DefaultStrategy.refine function in Experiment.run_once only gets training replies that are success. This is due to Job._get_training_result that does not add success = False replies into training_replies dictionary. This situation results as successful training round even when one or more than one node returns success=False if at least a node return successful training reply.

Simple solution can be to add unsuccessful reply to the training replies and let strategy class do the rest. However, this solution also requires to modify function _extract_received_optimizer_aux_var_from_round to only allow extraction for successful replies.