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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ソースファイル、テスト、コマンド、再現可能な手順は提供されていません。まず、CloudStack 4.18.1.0、XCP-NG、NFS バックのセカンダリストレージを使用して VM の起動失敗を再現します。ISO イメージをマウントしたときに永続的な空の ISO SRs を作成せずに VMs が起動すれば完了です。

索引モデルが issue の本文から書いたものです。