Merge pull request #69942 from ronen-fr/wip-rf-339463backfl

crimson/osd: fix backfill deadlock when only delete operations remain

Reviewed-by: Radoslaw Zarzynski <rzarzyns@redhat.com>
Reviewed-by: Matan Breizman <mbreizma@redhat.com>
Reviewed-by: Mohit Agrawal <moagrawa@redhat.com>