librbd: update progress for non-existent objects on deep-copy

librbd: update progress for non-existent objects on deep-copy

As a side effect of commit e5a21e904142 ("librbd: deep-copy image copy
state machine skips clean objects"), handle_object_copy() stopped being
called for non-existent objects.  This broke progress_object_no logic,
which expects to "see" all object numbers so that update_progress()
callback invocations can be ordered.  Currently update_progress() based
progress reporting gets stuck after encountering a hole in the image.

To fix, arrange for handle_object_copy() to be called for all object
numbers, even if ObjectCopyRequest isn't created.  Defer the extra call
to the image work queue to avoid locking issues.

Fixes: https://tracker.ceph.com/issues/56181
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
(cherry picked from commit 6813a7879146aec40f204a174b40a5a54e00b780)