ui: lvm-thin: fix not being able to edit the storage

ui: lvm-thin: fix not being able to edit the storage

The change handler of the edit config from a displayEditField still
triggers, even if hidden and disabled. This then enables another
editConfig part of a displayEditField, which triggers an error in the
API.

To fix that, simply check if this field is disabled before setting
the other fields value

Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>
Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>