adding a barrier after output folder creation

[dkazanc]

Fixes the issue of not having the output folder created for other ranks than 0.
I went the global_comm.Barrier() way as at this point in the run there shouldn't be much of racing going on and we're not loosing time on synchronisation? It fixes the problem in Jenkins tests and pipelines run.

Checklist

• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• I have made corresponding changes to the documentation
• I have added the user-release-note label in order to include this PR in the "Notable
  Changes for Users" section in release notes

[yousefmoazzam]

As mentioned in the team meeting, I think that adding a barrier is the correct way to resolve the race condition of the non-zero rank processes seeing the YAML file at all, or seeing the YAML file in the correct state.

Just needs the linting fixed and this is good to go, thanks! 🙂