Description of problem:
Start a vm, execute some operations that can produce taint message, then restart libvirtd and check dominfo, and found that Taint message generated during vm running is not preserved during libvirtd restart

Version-Release number of selected component (if applicable):
libvirt-7.3.0-1.module+el8.5.0+11004+f4810536.x86_64


How reproducible:
100%

Steps to Reproduce:
1. Start a vm

2. Execute some operations that can produce taint message, e.g.
1) Execute agent command
virsh qemu-agent-command $vm '{"execute": "guest-info"}'

2) Hotplug a cdrom type disk sourced by host block device
# virsh attach-disk avocado-vt-vm1 --source /dev/cdrom --type cdrom --sourcetype block --target hda

3) Hotplug a interface device with script
# virsh attach-device avocado-vt-vm1 net.xml
# cat net.xml 
<interface type='ethernet'>
<script path='/etc/qemu-ifup'/> 
</interface>


3. Check dominfo:
# virsh dominfo avocado-vt-vm1
Id:             4
Name:           avocado-vt-vm1
UUID:           fa26e276-1bb1-47eb-be0e-57e8bb8cf0d9
OS Type:        hvm
State:          running
...
Messages:       tainted: network configuration using opaque shell scripts
                tainted: potentially unsafe use of host CPU passthrough
                tainted: use of host cdrom passthrough
                tainted: custom guest agent control commands issued

4. Restart libvirtd

5. Check dominfo:
# virsh dominfo avocado-vt-vm1
Id:             4
Name:           avocado-vt-vm1
UUID:           fa26e276-1bb1-47eb-be0e-57e8bb8cf0d9
OS Type:        hvm
State:          running
...
Messages:       tainted: potentially unsafe use of host CPU passthrough


Actual results:
Taint message that are generated when vm starts is preserved during libvirtd restart, but not for those generated when vm is running

Expected results:
All taint messages should be preserved during libvirtd restart

Additional info: