In reftable/writer.c:padded_write(), if w->writer failed, zeroed
allocated in `reftable_calloc` will leak. w->writer could be
`reftable_write_data` in reftable/stack.c, and could fail due to
some write error. Simply add reftable_free(zeroed) will solve this
problem.
Signed-off-by: Lidong Yan <502024330056@smail.nju.edu.cn>
Signed-off-by: Junio C Hamano <gitster@pobox.com>