Fail to start VM from ISO

##### ISSUE TYPE

* Bug Report

##### COMPONENT NAME

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Secondary Storage
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##### CLOUDSTACK VERSION

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CloudStack 4.18.1.0
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##### CONFIGURATION

XCP-NG is used as hypervisor
Secondary storage connected via NFS
##### OS / ENVIRONMENT

##### SUMMARY

Hi!
I faced issue with ISO images.
Whe I mount ISO to multiple VMs, they stop starting in Cloudstack. And from the backend, I can see multiplying ISO SRs on every try to start VM. Some of them has ISO file inside, but most of them hasn't. Please look at screenshots attached.

My general question is can I safely remove (detach/foget/destroy) this empty SRs?
Even if I delete VM, ISO SRs still in the place.
Is there any way to fix issue with VM start?

Thank you in advance!

##### STEPS TO REPRODUCE

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##### EXPECTED RESULTS

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##### ACTUAL RESULTS

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未提供原始檔案、測試、命令或可重現的步驟。首先使用 CloudStack 4.18.1.0、XCP-NG 和以 NFS 為後端的次要儲存體重現 VM 啟動失敗；當掛載 ISO 映像時 VMs 能夠啟動，且不會建立持久的空 ISO SRs，即視為完成。

由索引模型根據 Issue 內容生成。