Disable replication version plugin by default.

The 389-ds replication plugin may not be installed on all platforms
and our replication version plugin will cause 389-ds to not start
if it is loaded and the replication plugin is not. So disable by
default.

When a replica is prepared we check for the replication plugin.
If it exists we will enable the replication version plugin.

Likewise on installation of a replica we check for existence of
the repliation plugin and if it is there then we enable the version
plugin before replication begins.

ticket 918

ipaserver/install/dsinstance.py

@@ -289,6 +289,10 @@ class DsInstance(service.Service):
 
 
     def __setup_replica(self):
+        replication.enable_replication_version_checking(self.fqdn,
+            self.realm_name,
+            self.dm_password)
+
         repl = replication.ReplicationManager(self.realm_name,
                                               self.fqdn,
                                               self.dm_password)