qemu-ga update resetting VssOption Registry key to default

As instructed by YanVugenfirer on Github, moving this issue here. https://github.com/virtio-win/virtio-win-guest-tools-installer/issues/77

Host environment

• Operating system: Proxmox 8.3.5
• OS/kernel version: 6.8.12-5-pve
• Architecture: x86

Emulated/Virtualized environment

• Operating system: Windows Server 2022, 2024/04 patch.
• Architecture: x86

Description of problem

Before I installed the .exe from iso virtio-win-0.1.271.iso, I had value 5 in registry key HKLM:\SYSTEM\CurrentControlSet\Services\QEMU Guest Agent VSS Provider\VssOption. After the driver update by the .exe, the value was set to 1.

This registry key shouldn't change in driver update, as its value was manually set to 5 and it is important to preserve MSSQL backups in Proxmox. Source: https://blog.datact.ch/backup-mssql-server-with-proxmox https://forum.proxmox.com/threads/pbs-breaking-customer-sql-backups-backups-without-fs-freeze.111526/

Steps to reproduce

1. Set a value to HKLM:\SYSTEM\CurrentControlSet\Services\QEMU Guest Agent VSS Provider\VssOption other than 1.
2. Install the .exe from version 0.1.271.
3. Check the key value.

Expected behavior

The registry key HKLM:\SYSTEM\CurrentControlSet\Services\QEMU Guest Agent VSS Provider\VssOption should preserve its value from before the driver update.