cls/rgw: rgw_dir_suggest_changes detects race with completion

cls/rgw: rgw_dir_suggest_changes detects race with completion

if bucket listing races with a pending index transaction, its suggested
removal may be mistakenly applied if that index transaction completes
before the osd receives this suggestion

in `rgw_dir_suggest_changes()`, the sole condition for applying a
suggested change is that the `cur_disk.pending_map` is empty. this is
true after rgw_bucket_complete_op()

on index completion, `rgw_bucket_dir_entry::index_ver` is updated to match
the new value of `rgw_bucket_dir_header::ver`. because most of `struct
rgw_bucket_dir_entry` makes the round trip through bucket listing ->
dir_suggest, we have access to the index_ver of the suggested entry. by
comparing this against the stored entry, we can ignore any suggestions
that were sent before the most recent completion

Fixes: https://tracker.ceph.com/issues/54528
Signed-off-by: Casey Bodley <cbodley@redhat.com>
(cherry picked from commit aa381b6765b0fb316976c4af7a45f32a157a4f75)