Description of problem: Back with YUM and it's "famous" yumdb, one could mark a specific package to be kept, even when the respective install_only_limit was reached: `yumdb set installonly keep EXACT_PKG_AND_VERSION_TO_KEEP`. That lead to the oldest non-marked version to be removed when installing a newer one after the install only limit was reached. Since the removal of YUMDB, there seems to be no such option anymore. While DNF has explicit handling code to ensure the running kernel is never removed, there is no way to ensure the same for other packages installed/marked as "installonly". Additional Note: - The general install-only feature works like charm - This is NOT the same as `versionlock` as updates should still be installed, but the running version needs to be kept (hence, the use of the install-only feature and, previously, setting the appropriate key in yumdb). - I looked into creating a plugin to provide this functionality but I cannot find a means to overrule the decision to simply remove the oldest variant of an installed package