Fix for issue 4172 (dsreplication: disable + enable causes SSL connection error)

The code assumed that if the two registries were equal, then they were replicated.  This was wrong, if we disabled replication for one server, only the disabled server was unregistered from the ADS and this caused the problem (since the certificate of the previously unregistered server was not seeded).  The fix consists of two parts (even though just one of them would be enough to fix the issue, I think that having both will help the code to handle more scenarios):

1. Check that if the registries are equal, they actually are replicated (in terms of configuration of the replication).
2. Unregister ALL the servers from the ADS of the server where replication is being disabled if we have to unregister the server itself.