copydir: fix impl usage

copydir: fix impl usage

    copydir.c: In function 'copy_dir':
    copydir.c:517:32: warning: passing argument 1 of 'copy_tree' from incompatible pointer type [-Wincompatible-pointer-types]
      517 |             return (copy_tree (src, dst, false, reset_selinux,
          |                                ^~~
          |                                |
          |                                const struct path_info *
    In file included from copydir.c:20:
    ../lib/prototypes.h:108:35: note: expected 'const char *' but argument is of type 'const struct path_info *'
      108 | extern int copy_tree (const char *src_root, const char *dst_root,
          |                       ~~~~~~~~~~~~^~~~~~~~
    copydir.c:517:37: warning: passing argument 2 of 'copy_tree' from incompatible pointer type [-Wincompatible-pointer-types]
      517 |             return (copy_tree (src, dst, false, reset_selinux,
          |                                     ^~~
          |                                     |
          |                                     const struct path_info *
    ../lib/prototypes.h:108:57: note: expected 'const char *' but argument is of type 'const struct path_info *'
      108 | extern int copy_tree (const char *src_root, const char *dst_root,
          |                                             ~~~~~~~~~~~~^~~~~~~~

Fixes: 74c17c71 ("Add support for skeleton files from /usr/etc/skel")