Volume Snapshot Fails After First Successful Snapshot – (XCP-ng 8.3, CloudStack 4.21)

### problem

We are encountering an issue while creating volume snapshots on VMs hosted on XCP-ng 8.3 with FC primary storage.
The first snapshot is created successfully, however any subsequent snapshot attempt fails.

Error
The snapshot job fails with the following error:
failed to getVhdParent with args isISCSI

### versions

Component Version
CloudStack 4.21
Hypervisor XCP-ng 8.3
Storage Type Pre-setup Storage over FC
Primary Storage Fibre Channel (FC)

### The steps to reproduce the bug

snapshot of the volume → Success.
Attempt to create the second snapshot of the same volume → Failure.

Logs:
[logs.txt](https://github.com/user-attachments/files/25788703/logs.txt)

### What to do about it?

_No response_

先閱讀附加的 logs.txt 並重現以下順序：建立一個磁碟區快照，然後在列出的 XCP-ng 和 FC 設定中，嘗試對同一個磁碟區建立第二個快照。追蹤快照路徑中回報的「getVhdParent with args isISCSI」錯誤。連續快照都能在沒有該錯誤的情況下成功，即表示完成。

由索引模型根據 Issue 內容生成。