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_

首先阅读随附的 logs.txt 并重现以下过程：创建一个卷快照，然后在所列出的 XCP-ng 和 FC 设置中尝试对同一卷创建第二个快照。跟踪快照路径中报告的“getVhdParent with args isISCSI”错误。连续快照能够成功完成且不出现该错误，即表示完成。

由索引模型根据 Issue 内容生成。