Fix --rpm-use-permissions stat call

The stat call in --rpm-use-permissions would remove the leading / from
all files, causing the stat to fail.  Changed the regex to not do that.
Also changed 'stat' to 'lstat', or rpm creation would bomb on broken
symlinks within the package.

There's no rspec included, but I tested the change with lots of rpm
creations.

Also, since directories aren't automatically included, they'll be set to
root:root unless --rpm-auto-add-directories is used.  Perhaps
--rpm-use-permissions should imply that?