dog/cluster: code optimize for confirmation of cluster_force_recover

reuse confirm() is better, no need to handle it from scratch.

Signed-off-by: Ruoyu <liangry@ucweb.com>
Reviewed-by: Hitoshi Mitake <mitake.hitoshi@lab.ntt.co.jp>
Signed-off-by: Liu Yuan <namei.unix@gmail.com>