service: add implicit dbus deps only for Type=dbus units

We want to be able to use BusName= in services that run during early boot
already, and thus don't synthesize deps on dbus there. Instead add them
when Type=dbus is set, because in that case we actually really need
D-Bus support.

Fixes: #17037

src/core/service.c

@@ -684,7 +684,7 @@ static int service_setup_bus_name(Service *s) {
 
         assert(s);
 
-        if (!s->bus_name)
+        if (s->type != SERVICE_DBUS)
                 return 0;
 
         r = unit_add_dependency_by_name(UNIT(s), UNIT_REQUIRES, SPECIAL_DBUS_SOCKET, true, UNIT_DEPENDENCY_FILE);