Fix unittests that relied on checksum being at the end of solvfiles

[kontura]

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[pep8speaks]

Hello @kontura! Thanks for updating this PR. We checked the lines you've touched for PEP 8 issues, and found:

There are currently no PEP 8 issues detected in this Pull Request. Cheers! 🍻

Comment last updated at 2022-03-01 11:47:46 UTC

[lukash]

It's not very pretty with using an unrelated repo .solv file to simulate checksum mismatch, but I guess it's good enough for dnf 4.

[kontura]

Alternatively we could add another new generated repo or edit the solvfile at a hard coded position by hand.
Using the already present drpm repo seemed like the lesser evil to me.

[lukash]

Let's keep it this way, should be good enough.