Use it for the save, delete, push testing for composer-cli
tests. Otherwise the test runs fine the first time and fails after that
if you don't re-install the test environment.
Related: rhbz#1678937
Stop using fake dnf object, use the real thing. This will help catch
problems with dnf returning unexpected types like VectorString.
(cherry picked from commit 27aff75aa3)
Related: rhbz#1655876