The previous fix in b41daecb5 was incomplete. Fixup entries are
given the original path without calling cleanup_pathname().
To make sure we don't follow a symlink, we must strip trailing
slashes from the path.
The fixup entries are always directories. Make sure we try to modify
only directories by providing O_DIRECTORY to open() (if supported)
and if it fails to check directory via lstat().
Resolves: #1996634
