On system with empty /boot (example: /boot on external device and not
mounted:
* `vkpurge list` reports `*`, which is incorrect, and
* `vkpurge rm all` run `remove_kernel` for all file names in $PWD,
this will normally harmless except when efibootmgr is used and some
files with special name, let's say "V" "o" "i" "d" in $PWD, then,
efibootmgr will remove all boot entries.
Fix it by checking for `vmlinu[xz]-*` explicitly.
A sane system shouldn't have that file.
b650ceec66