Add treeinfo/.treeinfo to index files

  When kickstarting a CentOS 7 system towards pkg-cacher I got the
  error "Sorry, not allowed to fetch that type of file: .treeinfo"
  and "Sorry, not allowed to fetch that type of file: treeinfo" in
  the pkg-cacher error.log. The OS installation aborts. After adding
  the files name to the pkg-cacher index files, anaconda is able
  to successfully recognise pkg-cacher as installation repository.