bindinstance: make sure zone manager is initialized in add_master_dns_records

Bind instance is configured using a short-circuited way when replica is set up.
Make sure required properties are in place for that.

https://fedorahosted.org/freeipa/ticket/4186

Reviewed-By: Petr Viktorin <pviktori@redhat.com>

ipaserver/install/bindinstance.py

@@ -831,6 +831,7 @@ class BindInstance(service.Service):
         self.reverse_zone = reverse_zone
         self.ca_configured = ca_configured
         self.first_instance = False
+        self.zonemgr = 'hostmaster.%s' % self.domain
 
         self.__add_self()
         self.__add_ipa_ca_record()