[SCSI] tgt: move tsk_mgmt_response callback to transport class

This moves tsk_mgmt_response callback in struct scsi_host_template to
struct scsi_transport_template since struct scsi_transport_template is
more suitable for the task management stuff.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: Mike Christie <michaelc@cs.wisc.edu>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>