A previous commit updated 17.xx -> 18.xx without considering
that some systems still use 17.xx.
Add handling for 17.0[3,6,9] as validated versions.
Also re-format the error message because the version is not validated
per maximum basis, but rather based on existing validation.
Clear Linux Project for Intel Architecture uses its own path
to store kernel build artifacts. This is documented, e.g.,
in https://github.com/clearlinux/clr-boot-manager.
Adapt kernel validator's config check paths to include Clear
Linux's path too.
