base-manager: start device support check on first port addition

This avoids the "port in device added after device probing has already
finished" warning, and also the creation of modem objects for single
port devices.

src/mm-base-manager.c

@@ -451,7 +451,10 @@ first_port (MMBaseManager  *self,
     }
 
     /* Store the device */
-    g_hash_table_insert (self->priv->devices, g_strdup (uid), g_steal_pointer (&device));
+    g_hash_table_insert (self->priv->devices, g_strdup (uid), g_object_ref (device));
+
+    /* And start device support check */
+    device_support_check_add_single_port (self, device, port);
 }
 
 static void