Incorrect error message while creating instance snapshot without memory for a stopped VM

### problem

Incorrect error message while creating instance snapshot without memory for a stopped VM (ROOT & DATA disk on different PowerFlex pools)

```
2026-04-10 09:43:05,535 DEBUG [c.c.v.s.VMSnapshotManagerImpl] (qtp698741991-25:[ctx-8948ca15, ctx-1e54ecb4]) (logid:ea105dce) Creating a snapshot of a running KVM Instance without memory is not supported
2026-04-10 09:43:05,536 INFO [c.c.a.ApiServer] (qtp698741991-25:[ctx-8948ca15, ctx-1e54ecb4]) (logid:ea105dce) Failed to create Instance Snapshot: Creating a snapshot of a running KVM Instance without memory is not supported
```

### versions

ACS 4.20.3 RC4 + Advanced Zone + KVM hypervisor

Should exist with 4.20.1 & 4.20.2 as well, as per the changes here:
https://github.com/apache/cloudstack/pull/9773/changes#diff-7d772616388f0b97219416327c6db1bcad3c162d0271f245ee903198913aa0d3

### The steps to reproduce the bug

1. Deploy a VM with data disk (ROOT & DATA disk on different PowerFlex pools)
2. Stop the VM
3. Take VM snapshot

### What to do about it?

Expecting correct state of the VM in the error message.

Instance snapshots without memory is supported with PowerFlex volumes when all volumes are on the PowerFlex storage and different pools (this seems broken here: https://github.com/apache/cloudstack/pull/3724/changes#diff-705d7f4f3bd1b9d599a38327738fab759b6f6a925f405cbbb7de7bef9b586be2) - now, it is supported when all the volumes are on the same PowerFlex pool only.

Inizia in VMSnapshotManagerImpl, dove il log segnala il messaggio errato relativo alla VM in esecuzione, e confronta il comportamento con le modifiche referenziate nei PR 9773 e 3724. Riproduci il caso di snapshot di una VM arrestata con dischi ROOT e DATA su pool PowerFlex diversi; il lavoro è completato quando l'errore riporta lo stato effettivo della VM e l'operazione supportata funziona correttamente.

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