If item_insert() or item_insert_order() failed to insert an item, they
would leak the item they had just created. This was causing runaway
memory consumption while running the iteration_check testcase, which
proves that Ross has too much memory in his workstation ;-)
Make sure to free the item on error. Found with -fsanitize=address.
Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com> Reviewed-by: Rehas Sachdeva <aquannie@gmail.com>