stop_buildx is blocking pipeline

From @balasankarc :

Doubt regarding buildx - when should the stop-buildx jobs be run on the following scenarios

1. MR pipelines
2. Master branch pipelines
3. Stable branch pipelines
4. Auto-deploy pipelines

For MR ones, I believe they should be run when MR is merged and branch is deleted, by the on_stop directive. But I am not sure about the others.

I suggested allowed to fail not because stop-buildx caused issues, but because without it manual jobs become blocking manual jobs that mark the pipeline status as blocked. This kinda affects any monitoring effort based on success/failed status of pipelines. Until gitlab-org/gitlab#382179 is done, this is an ugly thing we have to do so the pipeline statuses are correct. 😞