Log when oneshot commands finish

[jwodder]

As instructed in https://github.com/dandi/dandisets/issues/342#issuecomment-1500352762

[codecov[bot]]

Codecov Report

Patch coverage: 100.00% and project coverage change: +0.13 :tada:

Comparison is base (aff2cf3) 76.23% compared to head (df5e64f) 76.37%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## draft #343 +/- ## ========================================== + Coverage 76.23% 76.37% +0.13% ========================================== Files 14 14 Lines 2445 2451 +6 Branches 538 538 ========================================== + Hits 1864 1872 +8 Misses 431 431 + Partials 150 148 -2 ``` | [Impacted Files](https://codecov.io/gh/dandi/dandisets/pull/343?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=dandi) | Coverage Δ | | |---|---|---| | [tools/backups2datalad/aioutil.py](https://codecov.io/gh/dandi/dandisets/pull/343?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=dandi#diff-dG9vbHMvYmFja3VwczJkYXRhbGFkL2Fpb3V0aWwucHk=) | `74.74% <100.00%> (+0.78%)` | :arrow_up: | ... and [1 file with indirect coverage changes](https://codecov.io/gh/dandi/dandisets/pull/343/indirect-changes?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=dandi) Help us with your feedback. Take ten seconds to tell us [how you rate us](https://about.codecov.io/nps?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=dandi). Have a feature suggestion? [Share it here.](https://app.codecov.io/gh/feedback/?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=dandi)

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[yarikoptic]

looks good, thank you @jwodder !