Additional SCSI controllers are not set to "virtio-scsi" as requested

[Matt]

When adding virtio-scsi disks to a guest using virt-manager, the second and additional SCSI controllers are not added as virtio-scsi, thereby making the disks not gain the benefits of virtio-scsi.

To duplicate this issue:
1. On a VM with no SCSI disks of any type, add seven virtio-scsi disks to an existing VM ("Details" tab -> "Add Hardware" button -> "Select managed or other existing storage" -> Device type: Virtio SCSI disk)
2. Notice that the "Controller SCSI" listed at the bottom of the hardware list shows "Model: virtio-scsi".
3. Add one more virtio-scsi disk using the method described in step 1.
4. Look at the newest (second) "Controller SCSI" listed at the bottom of the hardware list. It will show "Model: Default", instead of "Model: virtio-scsi".
5. Run some form of disk benchmarking and notice the speed is slower on the disks attached to the second SCSI controller. Also notice that your virtio-scsi disks are able to be removed and added from a running VM, but not the ones on the "Default" SCSI controller, which will require a guest reboot.

Workaround:
After adding all of your disks, edit the domain XML with "virsh edit" and add:

  model="virtio-scsi"

to the SCSI controller. Save and exit, shutdown and relaunch the VM. You'll now gain the performance and hotplug abilities of virtio-scsi.

ProblemType: Bug
DistroRelease: Ubuntu 14.04
Package: virt-manager 0.9.5-1ubuntu3
ProcVersionSignature: Ubuntu 3.13.0-24.46-generic 3.13.9
Uname: Linux 3.13.0-24-generic x86_64
ApportVersion: 2.14.1-0ubuntu3
Architecture: amd64
Date: Mon Jun 9 14:18:36 2014
InstallationDate: Installed on 2014-04-24 (46 days ago)
InstallationMedia: Ubuntu-Server 14.04 LTS "Trusty Tahr" - Release amd64 (20140416.2)
PackageArchitecture: all
ProcEnviron:
 TERM=xterm
 PATH=(custom, no user)
 SHELL=/bin/bash
SourcePackage: virt-manager
UpgradeStatus: No upgrade log present (probably fresh install)