networkd: ndisc - consider configured on timeout

Don't block indefinitely, when control has been passed on from NDisc to DHCPv6.
In this case there is likely no IPv6 support on the local link, so otherwise
this would block indefinitely.

src/network/networkd-ndisc.c

@@ -207,6 +207,10 @@ static void ndisc_handler(sd_ndisc *nd, int event, void *userdata) {
                 r = sd_dhcp6_client_start(link->dhcp6_client);
                 if (r < 0 && r != -EALREADY)
                         log_link_warning_errno(link, r, "Starting DHCPv6 client after NDisc timeout failed: %m");
+
+                link->ndisc_configured = true;
+                link_check_ready(link);
+
                 break;
         case SD_NDISC_EVENT_STOP:
                 break;