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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Non vengono forniti file sorgente, test, comandi o passaggi riproducibili. Inizia riproducendo il fallimento dell'avvio della VM con CloudStack 4.18.1.0, XCP-NG e storage secondario basato su NFS; il lavoro è completato quando le VM si avviano montando immagini ISO senza creare ISO SRs vuoti persistenti.

Scritto dal modello di indicizzazione a partire dal testo della issue.