Remove unveil() from the rsync_sender() and flist_gen(). The sender is

Remove unveil() from the rsync_sender() and flist_gen(). The sender is
not able to properly unveil itself because you can request many files
as arguments. At the same time the sender is read-only and uses rpath
pledge() so the gain from unveil() is less of an issue.
On the receiver side all files land in one directory and this part still
uses unveil() to protect rsync to somehow walk out of the destination
directory.
From kristaps@