W&B ID reset on training completion (#1852)

* Update train.py

Fix the bug of always the same W&B ID  and continue  overwrite with the old logging.
BUG report
https://github.com/ultralytics/yolov5/issues/1851

* Fix the bug of duplicate W&B ID

fix the bug of https://github.com/ultralytics/yolov5/issues/1851
If we had trained on yolov5s.pt, the program will generate a new unique W&B ID.
If we hadn't, the program will keep the old code, we can still use --resume aug.

* Update general.py

* revert train.py changes

Co-authored-by: Glenn Jocher <glenn.jocher@ultralytics.com>

utils/general.py

@@ -361,8 +361,8 @@ def non_max_suppression(prediction, conf_thres=0.25, iou_thres=0.45, classes=Non
 def strip_optimizer(f='weights/best.pt', s=''):  # from utils.general import *; strip_optimizer()
     # Strip optimizer from 'f' to finalize training, optionally save as 's'
     x = torch.load(f, map_location=torch.device('cpu'))
-    x['optimizer'] = None
-    x['training_results'] = None
+    for key in 'optimizer', 'training_results', 'wandb_id':
+        x[key] = None
     x['epoch'] = -1
     x['model'].half()  # to FP16
     for p in x['model'].parameters():