Comment 4 for bug 1570304

Found a third error case: "Is a directory"

  plop@ubuntu:~/testtar/rr$ tar -xz --incremental -f ../level1
  tar: Cannot rename ‘./1/42/31’ to ‘./1/0’: Is a directory
  tar: Exiting with failure status due to previous errors

I'm still working on a way to reproduce easily this one "Is a directory" and the first one "No such file or directory".