Update pipeline_http_client.py

the second test_img_dir assignment is not necessary:
after it is defined,  it's not modified. We can use it anyway.

修复多线程调用下IndexError报错

Update predict_det.py

fix dead link for serving

cherry-pick #4823

I found that when I export model SAST to predict image, that made difference predict bounding box between inference model and train model

[cherry-pick] fix attn loss for ce

cp fix trt8 core bug

修复包导入错误

read_params应该从ocr_det而不是ocr_system中导入

add reference for locality_aware_nms