Ui/Api : Allow updating "Read Instance settings from OVA" true/false

[kiranchavala]

The required feature described as a wish

As a User/Admin/Operator I would like to have the ability to change template property

Steps to reproduce the issue

1. Register the template with "Read Instance settings from OVA"

2. Try to edit the template , there is no option to disable the "Read Instance settings from OVA""

If there are no instances deployed from the Template, Admin/User should be allowed to change the Template setting “Read Instance settings from OVA”