Plugin PR unittester installs unittests from master, but code from PR
Plugin pr unittest jobs are failing when both code and unittest changes are present. Unittests are installed from the master branch, but the code is installed from the PR.
This was originally fixed by installing all packages into the same venv: https://github.com/pulp/pulp-ci/pull/516
But that caused some issues: https://pulp.plan.io/issues/3684
We need to fix the environment and stop installing packages to different venv/system python locations