Ensure service is force Down when an error is raised during service syncing
Ensure cluster is initialized synchronously during the cluster startup

This prevent the server to start if there is an error while reading the cluster topology from Zookeeper.
Integration tests for service member sabotage
Merge branch 'master' into manu-zookeeper-sabotage
Increment a new sync error counter inestead of forcing all service members Down
Merge pull request #221 from wajam/manu-zookeeper-sabotage

Zookeeper service member sabotage fix