Fix typo in check_clones()

Run kmem_free() after zap_cursor_fini().

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Tino Reichardt <milky-zfs@mcmilk.de>
Reviewed-by: Adam Moss <c@yotes.com>
Signed-off-by: George Amanakis <gamanakis@gmail.com>
Closes #14702