Don't allow additon of template settings when the template is in Not-Ready state

### problem

Don't allow addition of template settings when the template is in Not-Ready state

### versions

ACS 4.22

### The steps to reproduce the bug

1. Login to cloudstack with a admin role

Navigate Images > Template > Register a template > enable “Read Instance settings from OVA”

2. When the template is getting downloaded , its in Not ready state

3. Navigate to template settings and try to add Template settings

4. The template settings gets added

### What to do about it?

CloudStack should thrown exception saying that its unable to add settings when the template is in not-ready state or Settings are read directly from the template

透過 Images > Template > 註冊一個已啟用「Read Instance settings from OVA」的範本，然後在範本處於 Not-Ready 狀態時嘗試新增範本設定，以重現此問題。追蹤範本設定的進入點及其驗證，並確認操作會以例外或訊息遭到拒絕，而不是新增設定。

由索引模型根據 Issue 內容生成。