[fix] add scope_name definition

[firedent]

1. Add scope_name definition into x2paddle/op_mapper/pytorch2paddle/aten.py. Missing scope_name will cause throwing NameError: name 'scope_name' is not defined when convert pytorch model file into paddlepaddle model file.
2. remove some unused variables in x2paddle/op_mapper/pytorch2paddle/aten.py
3. The outputs parameter of function graph.add_layer should be layer_outputs not current_outputs.

下面的文字请保留在PR说明的最后面，并在提完PR后，根据实际情况勾选确认以下情况

Please check the follow step before merging this pull request

• Python code style verification
• Review all the code diff by yourself
• All models(TensorFLow/Caffe/ONNX/PyTorch) testing passed
• Details about your pull request, releated issues

If this PR add new model support, please update model_zoo.md and add model to out test model zoos(@wjj19950828)

• New Model Supported
• No New Model Supported

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[jiangjiajun]

Hi, @firedent

Thanks for your contribution! Could you add some explanations for this pull request?

[firedent]

Hi, @jiangjiajun
Please check the update

1. Add scope_name definition into x2paddle/op_mapper/pytorch2paddle/aten.py. Missing scope_name will cause throwing NameError: name 'scope_name' is not defined when convert pytorch model file into paddlepaddle model file.
2. remove some unused variables in x2paddle/op_mapper/pytorch2paddle/aten.py
3. The outputs parameter of function graph.add_layer should be layer_outputs not current_outputs.

下面的文字请保留在PR说明的最后面，并在提完PR后，根据实际情况勾选确认以下情况

Please check the follow step before merging this pull request

• Python code style verification
• Review all the code diff by yourself
• All models(TensorFLow/Caffe/ONNX/PyTorch) testing passed
• Details about your pull request, releated issues

If this PR add new model support, please update model_zoo.md and add model to out test model zoos(@wjj19950828)

• New Model Supported
• No New Model Supported