rbd-mirror: fix image replayer shut down description on force promote

rbd-mirror: fix image replayer shut down description on force promote

On force promote if the opposite site is down then we currently show
image status description as "local image linked to unknown peer"

Previously:
----------
$ rbd --cluster=site-b mirror image status pool1/img1
img1:
  global_id:   a73341a6-8302-4c97-ac6e-278083fd347e
  state:       up+stopping_replay
  description: local image linked to unknown peer
  service:     admin on localhost.localdomain
  last_update: 2023-06-15 19:47:45
  peer_sites:
    name: site-a
    state: up+stopped
    description: local image is primary
    last_update: 2023-06-15 19:47:32
  snapshots:
    9 .mirror.primary.a73341a6-8302-4c97-ac6e-278083fd347e.1f101367-277f-42f0-8308-e51201d0529a (peer_uuids:[c46c6d97-f59b-4591-9d35-d7ff9d0d72f7])

Currently:
---------
$ rbd --cluster=site-b mirror image status pool1/img1
img1:
  global_id:   2a6d61e1-8e76-42c4-af76-8f61ce65c7e2
  state:       up+stopped
  description: orphan (force promoting)
  service:     admin on localhost.localdomain
  last_update: 2023-06-15 19:29:22
  peer_sites:
    name: site-a
    state: down+stopped
    description: local image is primary
    last_update: 2023-06-15 19:29:05
  snapshots:
    9 .mirror.primary.2a6d61e1-8e76-42c4-af76-8f61ce65c7e2.99f82a30-0241-4e51-8428-7a2376d137f6 (peer_uuids:[3150c6ef-aeee-45dc-8d0e-5dc5a53d88eb])

Fixes: https://tracker.ceph.com/issues/52913
Signed-off-by: Prasanna Kumar Kalever <prasanna.kalever@redhat.com>