logind: prefix some calls to unlink with (void)

Make Coverity happy and tell it we're not interested in the return
value of these two calls.

src/login/logind-dbus.c

@@ -1965,7 +1965,7 @@ static int method_cancel_scheduled_shutdown(sd_bus_message *message, void *userd
         m->scheduled_shutdown_timeout = 0;
 
         if (m->unlink_nologin) {
-                unlink("/run/nologin");
+                (void) unlink("/run/nologin");
                 m->unlink_nologin = false;
         }
 

src/login/logind.c

@@ -170,7 +170,7 @@ static void manager_free(Manager *m) {
                 udev_unref(m->udev);
 
         if (m->unlink_nologin)
-                unlink("/run/nologin");
+                (void) unlink("/run/nologin");
 
         bus_verify_polkit_async_registry_free(m->polkit_registry);