Description of problem:
Failed to add a new disk to VM using VirtIO-SCSI interface.
I tried both UI and REST-API.
The error is:
"Cannot attach Virtual Disk. VirtIO-SCSI is disabled for the VM"

If I try to create the VM along with the disk, the VM is created but without any disks. The error pops up just after the VM was created.

Version-Release number of selected component (if applicable):
ovirt-engine-4.4.0-0.19.master.el7.noarch
vdsm-4.40.2-1.el8ev.x86_64

How reproducible:
100%

Steps to Reproduce (using UI):
1. Create a new VM with a disk (Set the disk interface to be "VirtIO-SCSI")
2. 
3.

Steps to Reproduce (using REST-API):
1. Create a new disk (can be using the UI)
2. POST request to:
https://<engine>/ovirt-engine/api/vms/<vm_id>/diskattachments

Request body:

<disk_attachment>
    <active>true</active>
    <interface>virtio_scsi</interface>
    <disk id="<disk_id>">
        <read_only>false</read_only>
    </disk>
</disk_attachment>

Actual results:
Failed to attach the disk to the VM

Expected results:
The disk should be attached successfully

Additional info: