Not enough space on /boot due to failed upgrade attempt

[brianjmurrell]

Actual behavior

Upgrade has been inhibited due to the following problems:
    1. Not enough space on /boot

But it only is the case because initramfs-upgrade.x86_64.img and vmlinuz-upgrade.x86_64 exist from a prior failed leapp boot. leapp upgrade should either discount those files from the space check (since their space will be recovered when leapp upgrade overwrites them) or just remove them before doing the space check.