os/bluestore: use swap for deferred_stable when not bluefs_layout.single_shared_device()

os/bluestore: use swap for deferred_stable when not bluefs_layout.single_shared_device()

Fixes: https://tracker.ceph.com/issues/55608
When `bluefs_layout.single_shared_device()` is false and `deferred_done` is not empty, the `deferred_stable_queue` is always empty which make `deferred_stable` empty also.
So we can use swap instead of insert when insert key of `deferred_done` to `deferred_stable`.

Signed-off-by: wangyunqing <wangyunqing@inspur.com>