tests/functional: test a case of orphan object revival

Tested-by: Valerio Pachera <sirio81@gmail.com>
Signed-off-by: Hitoshi Mitake <mitake.hitoshi@lab.ntt.co.jp>
sheep: forbid revival of orphan objects

Current recovery process can cause revival of orphan objects. This
patch solves this problem.

How to: exclude a newly joining sheep from recovery process if a
cluster is already in SD_STATUS_OK. It emans the cluster has every
replica already.

Tested-by: Valerio Pachera <sirio81@gmail.com>
Signed-off-by: Hitoshi Mitake <mitake.hitoshi@lab.ntt.co.jp>