VM instance snapshot fails if "Quiesce Instance" snapshot parameter is true

### problem

When I try to take a VM instance snapshot setting "Quiesce Instance" to true the snapshot fails with the following error:
Failed to create vm snapshot: [VMSnapshot {"id":20,"name":"i-4-21-VM_VS_20260320122510","uuid":"e9760223-4c3e-4d79-b900-00b01c2f5884","vmId":21}] due to: can't handle quiescevm equal true for volume snapshot

The VM snapshot succeeds only if I disable the "Quiesce Instance" option.
But even if quiescence option is disabled I can see that inside the VM the guest agent fsfreeze and fsthaw hooks are called.
> Mar 20 13:33:21 sonia qemu-ga[11874]: info: guest-fsfreeze called
> Mar 20 13:33:23 sonia qemu-ga[11874]: info: guest-fsthaw called

So it seems that "Quiesce Instance" option is active anyway.

### versions

CloudStack 4.22.0
KVM hypervisor
Ceph storage
Rocky Linux 10

### The steps to reproduce the bug

1. select "Take Instance Snapshot" for a VM
2. set "Quiesce Instance" to true and press OK

### What to do about it?

_No response_

先檢視連結的 pull request #13941 及其修改的 snapshot 路徑，然後使用 "Quiesce Instance" 選項在 Ceph 上的 KVM VM 中重現失敗。完成的條件是：在啟用 quiescence 的情況下，要求的 snapshot 成功，且觀察到的 guest agent freeze/thaw 行為由該變更或其測試涵蓋。

由索引模型根據 Issue 內容生成。