Description of problem: After running "leapp preupgrade" check there's roughly 1G of leapp data left behind in /var/lib/leapp. Please either cleanup this data by default after preupgrade check or provide an option to do that so that no extra disk space is consumed after a preupgrade check. Thanks.
Added new step to the documentation informing people to do cleaning manually after the upgrade, with the note that after cleaning is done, investigation of any issues related to in-place upgrade will be nearly impossible.