Description of problem:
Qemu 6.0.0+ cannot use block device with 'file' driver due to this commit: https://github.com/qemu/qemu/commit/8d17adf34f501ded65a106572740760f0a75577c

VDSM needs to use host_cdrom/host_device instead of file. Alternatively this commit to qemu needs to be reverted.

Affected components:
libvirt.x86_64-7.6.0-2.el8s
qemu-kvm-6.0.0-29.el8s
vdsm-4.40.80.6-1.el8

Error information:
2021-09-24 17:15:26,391+0300 ERROR (jsonrpc/3) [virt.vm] (vmId='dea59d32-bb5e-4b60-be8a-468869798010') Forceful device flags update failed. (vm:5007)
Traceback (most recent call last):
  File "/usr/lib/python3.6/site-packages/vdsm/virt/vm.py", line 5005, in _update_disk_device
    disk_xml, libvirt.VIR_DOMAIN_DEVICE_MODIFY_FORCE)
  File "/usr/lib/python3.6/site-packages/vdsm/virt/virdomain.py", line 101, in f
    ret = attr(*args, **kwargs)
  File "/usr/lib/python3.6/site-packages/vdsm/common/libvirtconnection.py", line 131, in wrapper
    ret = f(*args, **kwargs)
  File "/usr/lib/python3.6/site-packages/vdsm/common/function.py", line 94, in wrapper
    return func(inst, *args, **kwargs)
  File "/usr/lib64/python3.6/site-packages/libvirt.py", line 3233, in updateDeviceFlags
    raise libvirtError('virDomainUpdateDeviceFlags() failed')
libvirt.libvirtError: internal error: unable to execute QEMU command 'blockdev-add': 'file' driver requires '/rhev/data-center/mnt/blockSD/aba0469b-e867-4e1c-8d34-cacf686e71d2/images/b7fd6e86-0d4a-4223-ad36-1b464da427a6/4884c4bd-c513-4741-9809-0a0de9e5cfb2' to be a regular file


Steps to Reproduce:
1. Start VM
2. Change to ISO which resides on Data Domain

Actual results:
ISO is not attaching to VM and user receives an error.

Expected results:
ISO is attached to VM