vhost-scsi: Add missing virtio-scsi -> TCM attribute conversion

While looking at hch's recent conversion to drop the MSG_*_TAG
definitions, I noticed a long standing bug in vhost-scsi where
the VIRTIO_SCSI_S_* attribute definitions where incorrectly
being passed directly into target_submit_cmd_map_sgls().

This patch adds the missing virtio-scsi to TCM/SAM task attribute
conversion.

Cc: Christoph Hellwig <hch@lst.de>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: stable@vger.kernel.org # 3.5
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>