CKL import allow-for- or warn-then-allow-hostname-only when FQDN field isn't standard

When importing CKL into Heimdall (or using the underlying hdf-converter for either SAF-CLI or Heimdall), allow for a single-word hostname.

Current behavior is to accept either blank or a.b.c.d format, but unfortunately many checklists in the wild don't follow these strictly, but allowing for a single hostname too should alleviate most loading rejections.