Add a few more user state dirs made by actual user creation in provision user helper

[jonasbardino]

Add a few more user state dirs made by actual user creation and importantly expected e.g. during useradm operations like edit_user, delete_user, etc. and therefore difficult to do without when adding test coverage a.o. in #561. Introduce two more common DNs used across tests: Other User and No Such User.
Polish a long comment with some typos and incomplete ending.

[albu-diku]

That's a good place to do it I think - just double checked and the last set of changes in the area did unify on the ..._dirs function as I'd remembered.

Two ideas - it might be worth having a constant that lists which keys of users to loop over calling mkdir, the idea would be keep similarity with _USERADM_PATH_KEYS. The second is creating there directories unconditionally means a bunch of ensure_dirs_exist calls in the tests for the corresponding dirs are no longer needed and I wonder if it is worth cleaning those up here as well (mostly to save any confusion in the future).

[jonasbardino]

That's a good place to do it I think - just double checked and the last set of changes in the area did unify on the ..._dirs function as I'd remembered.

Two ideas - it might be worth having a constant that lists which keys of users to loop over calling mkdir, the idea would be keep similarity with _USERADM_PATH_KEYS. The second is creating there directories unconditionally means a bunch of ensure_dirs_exist calls in the tests for the corresponding dirs are no longer needed and I wonder if it is worth cleaning those up here as well (mostly to save any confusion in the future).

Thanks for the review and insights @albu-diku . I've added comments to link to the _USERADM_PATH_KEYS variable and a TODO about cleaning up old related _ensure_dirs_exist for a later occasion, as I've already taken too many detours from the main PR :-s