Add systemctl daemon-reload to fix Ubuntu 16.04.1 warning

doc/update/8.12-to-8.13.md

@@ -166,6 +166,10 @@ See [smtp_settings.rb.sample] as an example.
 Ensure you're still up-to-date with the latest init script changes:
 
     sudo cp lib/support/init.d/gitlab /etc/init.d/gitlab
+    
+For Ubuntu 16.04.1 LTS:
+
+    sudo systemctl daemon-reload
 
 ### 9. Start application