midx-write: put failing response value back
This instance of setting the result to 1 before going to cleanup was
accidentally removed in fcb2205b77 (midx: implement support for writing
incremental MIDX chains, 2024-08-06). Build upon a test that already deletes
a packfile to verify that this error propagates to full command failure.
Signed-off-by: Derrick Stolee <stolee@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
authored by