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

通过 Images > Template > 注册一个启用了“Read Instance settings from OVA”的模板，然后在模板处于Not-Ready状态时尝试添加模板设置，以重现此问题。追踪模板设置的入口及其验证，并确认操作会通过异常或消息被拒绝，而不是添加设置。

由索引模型根据 Issue 内容生成。