OvmfPkg: turn off 'LUN encoding in CDB' SCSI feature
    
    This feature of UefiScsiLib violates the SBC-3, and is rejected by QEMU
    (post commit 96bdbbab, part of v1.2.0).
    
    Unless disabled, the feature breaks virtio-scsi block devices with
    non-zero LUNs.
    
    RHBZ: https://bugzilla.redhat.com/show_bug.cgi?id=1166971
    Reported-by: Cole Robinson <crobinso@redhat.com>
    Contributed-under: TianoCore Contribution Agreement 1.0
    Signed-off-by: Laszlo Ersek <lersek@redhat.com>