rpl: node-to-node communication broken (rpl_udp)

Calling ipv6_iface_set_srh_indicator with storing mode breaks the
neighbour discovery code in **ip.c:480**.
Thus, it is not possible to use `send <n> test` from node to node.

sys/net/routing/rpl/rpl.c

@@ -102,7 +102,9 @@ uint8_t rpl_init(int if_id)
     ipv6_addr_set_link_local_prefix(&ll_address);
     ipv6_net_if_get_best_src_addr(&my_address, &ll_address);
     ipv6_register_rpl_handler(rpl_process_pid);
+#if (RPL_DEFAULT_MOP == RPL_NON_STORING_MODE)
     ipv6_iface_set_srh_indicator(rpl_is_root);
+#endif
     ipv6_iface_set_routing_provider(rpl_get_next_hop);
     DEBUGF("All addresses set!\n");