When rfkill is disabled, resync the carrier state to be safe.

This change guards against possible regressions introduced by
f3766990f9 if rfkill were to
prevent netlink carrier up events from being delivered while
rfkill is in effect for the interface.

ndhc.c

@@ -334,6 +334,7 @@ static void do_ndhc_work(void)
         } else if (sev_rfk == RFK_DISABLED) {
             rfkill_set = 0;
             log_line("rfkill: radio now unblocked");
+            cs.carrier_up = ifchange_carrier_isup();
             if (rfkill_nl_carrier_wentup && carrier_isup()) {
                 // We might have changed networks while the radio was down.
                 force_fingerprint = true;