webadmin: disk interfaces - filter VirtIO-SCSI

New/Edit disk dialog:
filter out VirtIO-SCSI from disk interface list when
VirtIO-SCSI is disabled for the VM.

Change-Id: I07a1b9af5d8c7a0e4dc6f8cc40410b629d201fc4
Bug-Url: https://bugzilla.redhat.com/1014491
Signed-off-by: Daniel Erez <derez@redhat.com>