ProgramDesc copy doesn't handle BLOCKS attr type
Created by: panyx0718
https://github.com/PaddlePaddle/Paddle/blob/develop/paddle/fluid/framework/program_desc.cc#L77
Only handle BLOCK, but not BLOCKS
Created by: panyx0718
https://github.com/PaddlePaddle/Paddle/blob/develop/paddle/fluid/framework/program_desc.cc#L77
Only handle BLOCK, but not BLOCKS