Description of problem:
VM of Windows XP type gets virtio-scsi controller when created as a brand-new VM or from template. VMs created in earlier RHEV builds don't have this issue. The device is added by engine because vmCreate received by vdsm contains this device:
{'device': 'scsi', 'specParams': {}, 'model': 'virtio-scsi', 'type': 'controller', 'deviceId': 'dde43c41-8479-476b-959c-3c5493a9e39d'}
The issue is cosmetic but ugly - device manager shows a device with yellow exclamation mark and you can't get a driver for it.

Version-Release number of selected component (if applicable):
is25 / rhevm-backend-3.3.0-0.37.beta1.el6ev.noarch

How reproducible:
always

Steps to Reproduce:
1. create a VM of Windows XP OS Type
2. run the VM
3. look at its domain xml (or to vdsm logs at its vmCreate command)

Actual results:
vmCreate contains entry as above
domain xml contains device:
    <controller type='scsi' index='0' model='virtio-scsi'>
      <alias name='scsi0'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x04' function='0x0'/>
    </controller>

Expected results:
virtio-scsi is not added to Windows XP VMs (or VMs of any type lacking virtio-scsi driver)

Additional info:
VMs created in earlier builds are not affected