utimens: let lutimens work on non-symlinks

utimens: let lutimens work on non-symlinks

Coreutils new 'touch -h' is easier to write if we guarantee POSIX
semantics of utimensat(fd,"file",NULL,AT_SYMLINK_NOFOLLOW), rather
than blindly failing with ENOSYS even on non-symlinks.

* lib/utimens.c (lutimens): Fall back to utimens rather than
failing with ENOSYS, when file is not a symlink.
(utimens): Reduce redirection.
* tests/test-lutimens.h (test_lutimens): Update test to cover
non-symlinks.
* tests/test-utimens.h (test_utimens): Update test to cover
symlinks.
* tests/test-utimens.c (main): Update caller.

Signed-off-by: Eric Blake <ebb9@byu.net>