timesyncd: only attempt to connect when an address is configured

For now, we accept both link-local and routable addresses, maybe we want to
restrict ourselves to routable addresses only.

TODO

@@ -40,7 +40,6 @@ Features:
 
 * timesyncd:
   - hookup with networkd: NTP servers from dhcp
-  - hookup with networkd: listen to online/offline state
 
 * a way for container managers to turn off getty starting via $container_headless= or so...
 

src/timesync/timesyncd.c

@@ -1070,7 +1070,7 @@ static bool network_is_online(void) {
         int r;
 
         r = sd_network_get_operational_state(&state);
-        if (r >= 0 && streq("carrier", state))
+        if (r >= 0 && (streq("routable", state) || streq("degraded", state)))
                 return true;
         else
                 return false;