Minor error fixes for performing inference

[enesmsahin]

• Modified image destination path since current path requires root access to call os.makedirs("/results").
• Returned tensor_batch from inference(im, model, class_list, args) function since it is to be used in example loss calculation.
• Removed double display of the output image.
• Replaced torch._C.set_grad_enabled() calls with torch.set_grad_enabled() since it throws following AttributeError with PyTorch version 1.10.1:

AttributeError: module 'torch._C' has no attribute 'set_grad_enabled'