webadmin: VmGuideModel DirectLUN disk setLunType

VmGuideModel - when adding a DirectLUN disk
set LunType according to the selected StorageType
(as done in DiskListModel and VmDiskListModel).

Change-Id: I4499ee37556885663c89a29f530ad2d6db97cd51
Bug-Url: https://bugzilla.redhat.com/910562
Signed-off-by: Daniel Erez <derez@redhat.com>