tcm_loop: Fixup tag handling

The SCSI command tag is set to the tag assigned from the block
layer, not the SCSI-II tag message. So we need to convert
it into the correct SCSI-II tag message based on the
device flags, not the tag value itself.

Signed-off-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Sagi Grimberg <sagig@mellanox.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>