make sure to clean-up depth-first

[b97pla]

What problems does this PR solve?

There was a problem where the service would not properly clean up files and folders not included in the tar archive. This should fix that problem by ensuring that the content is cleaned up depth-first.

Also, the commands are wrapped in bash scripts rather than executed directly. This is not strictly necessary since this was intended to solve an issue with the executing shell but it didn't and therefore another workaround was used. However, it may be useful for troubleshooting to explicitly write the commands to scripts so I'll leave it in for now.

How has the changes been tested?
The unit tests have been run. Ideally, a bit more unit tests could be added but this is not done in this PR.

Reasons for careful code review
If any of the boxes below are checked, extra careful code review should be inititated.

• This PR contains code that could remove data

[Aratz]

Great work! Looks like this was a tricky problem. I agree there could be more tests (in particular to make sure that the bug we found in staging is solved) but that maybe this time we can let it go.

Had just one comment about adding a couple comments.