[v7r3] Fix: reintroducing Staging to Checking transition

[michmx]

BEGINRELEASENOTES

*WorkloadManagement
FIX: reintroduce 'Staging' to 'Checking' transition in JobsStateMachine

ENDRELEASENOTES

[andresailer]

Looks good to me!

[DIRACGridBot]

Sweep summary

Sweep ran in https://github.com/DIRACGrid/DIRAC/actions/runs/5667074899

Failed:

• rel-v8r0
  cherry-pick 7ac08b7 into rel-v8r0 failed
  check merge conflicts on a local copy of this repository

  git fetch upstream
  git checkout upstream/rel-v8r0 -b cherry-pick-2-7ac08b7be-rel-v8r0
  git cherry-pick -x -m 1 7ac08b7be
  # Fix the conflicts
  git cherry-pick --continue
  git commit --amend -m 'sweep: #7122 Fix: reintroducing Staging to Checking transition' --author=''
  git push -u origin cherry-pick-2-7ac08b7be-rel-v8r0
  
  # If you have the GitHub CLI installed the PR can be made with
  gh pr create \
       --label 'sweep:from rel-v7r3' \
       --base rel-v8r0 \
       --repo DIRACGrid/DIRAC \
       --title '[sweep:v8r0] Fix: reintroducing Staging to Checking transition' \
       --body 'Sweep #7122 `Fix: reintroducing Staging to Checking transition` to `rel-v8r0`.
  
  Adding original author @michmx as watcher.
  
  BEGINRELEASENOTES
  
  *WorkloadManagement
  FIX: reintroduce '"'"'Staging'"'"' to '"'"'Checking'"'"' transition in JobsStateMachine
  
  ENDRELEASENOTES
  Closes #7125'