webadmin: disable virtio-scsi for unsupported OSes

VM dialog:
* When selecting an OS that doesn't support VirtIO-SCSI,
  'VirtIO-SCSI Enabled' checkbox should be disabled.
* Updated VmModelBehaviorBase and derived behavior models accordingly.

Change-Id: I0256b84e1c82a6c2330287f1e68385d785d26b26
Bug-Url: https://bugzilla.redhat.com/1038613
Signed-off-by: Daniel Erez <derez@redhat.com>