Tests: fix test_forward_zones in test_xmlrpc/test_dns_plugin
    
    Class test_forward_zones in ipatests/test_xmlrpc/test_dns_plugin
    had server IP and zone name interchanged in "expected" dictionart.
    
    I do not understand how this happened.
    
    https://fedorahosted.org/freeipa/ticket/6213
    
    Reviewed-By: Martin Basti <mbasti@redhat.com>
    Reviewed-By: Stanislav Laznicka <slaznick@redhat.com>