Permit non-existent %ghost directories to be packaged (RhBug:839656)

Permit non-existent %ghost directories to be packaged (RhBug:839656)

- Directories can be explicitly specified via either %dir or trailing
  slash in the %files manifest, take this into account for %ghosts that
  dont exist in the buildroot. Otherwise we still assume regular file.
- Dont require explicit %attr() for missing %ghosts, let them fall
  back to %defattr() instead. If %defattr() doesn't specify a mode
  the file will be seen without any permissions at all, but that's
  not strictly an error (and same can happen with %dev() already)