This bug was introduced by https://github.com/redis/redis/issues/13814
When defragmenting `db->expires`, if the process exits early and
`db->expires` was modified in the meantime (e.g., FLUSHDB), we need to
check whether the previously defragmented expires is still the same as
the current one when resuming. If they differ, we should abort the
current defragmentation of expires.
However, in https://github.com/redis/redis/issues/13814, I made a
mistake by using `db->keys` and `db->expires`, as expires will never be
defragged.
debing.sun
2467eff59a