op buffer

config/ppo_transfer/3DBall.yaml

       action_feature_size: 32
       reuse_encoder: true
       in_epoch_alter: false
-      use_op_buffer: false
+      use_op_buffer: true
       use_var_predict: true
       with_prior: false
       predict_return: true

config/ppo_transfer/3DBallHard.yaml

       action_feature_size: 32
       reuse_encoder: true
       in_epoch_alter: false
-      use_op_buffer: false
+      use_op_buffer: true
       use_var_predict: true
       with_prior: false
       predict_return: true

config/ppo_transfer/3DBallHardTransfer.yaml

       action_feature_size: 32
       reuse_encoder: true
       in_epoch_alter: false
-      use_op_buffer: false
+      use_op_buffer: true
       use_var_predict: true
       with_prior: false
       predict_return: true