IOPs settings not applied when disk offering changes

### problem

Hi all.

In our PoC installation, I configured two disk offerings with different IOPs limits (1,000 and 10,000).
When I launch a test VM, the limit is applied correctly.
```xml

10000
10000

```
While the VM is running, I can change the offering, and a success message is displayed. Everything also looks successful in the management-server.log.
```
2026-05-19 16:31:47,618 DEBUG [o.a.c.f.j.i.AsyncJobManagerImpl] (API-Job-Executor-58:[ctx-e71e416f, job-1276, ctx-ee83f22a]) (logid:2c9eb69a) Complete async job-1276, jobStatus: SUCCEEDED, resultCode: 0, result: org.apache.cloudstack.api.response.VolumeResponse/volume/{"id":"d8a513c5-6241-46a9-b0d8-f969a5a245ce","name":"ROOT-61","zoneid":"57a96360-8053-487c-9fb9-85af87ca697d","zonename":"lc01","type":"ROOT","deviceid":"0","virtualmachineid":"e90057c4-5be9-492e-a78f-dfbca7507e07","templateid":"4c6bfba7-2457-466e-8767-7b3e620bb4e5","templatename":"Win2025-test2","templatedisplaytext":"Win2025-test2","vmname":"test-win02","vmdisplayname":"test-win02","vmstate":"Running","vmtype":"User","provisioningtype":"thin","size":"(50.00 GB) 53687091200","created":"2026-05-18T13:21:38+0200","state":"Ready","account":"admin","domainid":"b6a1560b-2912-11f1-af58-0050560103cb","domain":"ROOT","domainpath":"ROOT","diskIopsReadRate":"1000","diskIopsWriteRate":"1000","diskkbsread":"(1.33 MB) 1394345","diskkbswrite":"(43.25 KB) 44290","diskioread":"(52.04 KB) 53286","diskiowrite":"(3.00 KB) 3076","diskofferingid":"1b621070-6092-4d6e-91e1-987e662f2dd1","diskofferingname":"disk-1000","diskofferingdisplaytext":"disk-1000","destroyed":"false","isextractable":"false","displayvolume":"true","quiescevm":"false","supportsstoragesnapshot":"false","deleteprotection":"false","tags":[],"hasannotations":"false"}
```
However, the configuration of the VM on the KVM host remains the same.
```xml

10000
10000

```
The limit is only applied if I completely power down the VM and then power it back on.
Is there a trick to this, or something I've missed?

### versions

ACS 4.22.0
KVM/Qemu on Ubuntu 24.04

### The steps to reproduce the bug

1.
2.
3.
...

### What to do about it?

_No response_

Tái hiện sự cố trên ACS 4.22.0 với KVM/QEMU trên Ubuntu 24.04, bằng cách chuyển một VM đang chạy giữa các Disk Offering có giới hạn IOPS khác nhau. So sánh kết quả trong management-server.log với XML trực tiếp của VM trước và sau khi thay đổi; hoàn tất khi các giá trị iotune của VM đang chạy thay đổi mà không cần tắt VM.

Do mô hình lập chỉ mục viết ra từ nội dung của issue.