Currently the method of installing a package in the VM that needs its own repository (like fedora-updates) involves downloading the package to a separate folder and installing it using the install_additional_packages function from createdisk_library.sh, which creates a local repository of packages.
If we need to remove the repository (fedora-updates), there is a problem, since it breaks rpm-ostree, which requires all installed packages to be still resolvable (#1119).
However, install_additional_packages downloads the packages on the host first, and uploads them to the VM, which fails if there are packages that are available in repositories enabled only in the VM.