Fix #176 & #180: Replication does not always start at slave replica startup

Explicitly iterate true list of service members when starting ConcurentMasterSlave. At that time, the complete list of service members is known (#180). Also prevent log corruption by verifying the if the service member has already a subscription before initiating the recovery process (#176). The subscribe logic of ConcurentMasterSlave into an internal Actor to prevent race condition and deadlocks. 

As a bonus, the subscribe delay is now configurable.