qla2xxx: Fix incorrect tcm_qla2xxx_free_cmd use during TMR ABORT

This patch drops two incorrect usages of tcm_qla2xxx_free_cmd()
during TMR ABORT within tcm_qla2xxx_handle_data_work() and
tcm_qla2xxx_aborted_task(), which where attempting to dispatch
into workqueue context to do tcm_qla2xxx_complete_free() and
subsequently invoke transport_generic_free_cmd().

This is incorrect because during TMR ABORT target-core will
drop the outstanding se_cmd->cmd_kref references once it has
quiesced the se_cmd via transport_wait_for_tasks(), and in
the case of qla2xxx it should not attempt to do it's own
transport_generic_free_cmd() once the abort has occured.

As reported by Pascal, this was originally manifesting as a
BUG_ON(cmd->cmd_in_wq) in qlt_free_cmd() during TMR ABORT,
with a LIO backend that had sufficently high enough WRITE
latency to trigger a host side TMR ABORT_TASK.

In addition, for the case in tcm_qla2xxx_write_pending_status()
and tcm_qla2xxx_handle_data_work() that waits for outstanding
FCP WRITE data transfer to complete before preceeding with a
TMR ABORT, avoid se_cmd->t_transport_stop_comp that is already
used by transport_wait_for_tasks() and use a qla2xxx internal
struct completion instead.

Reported-by: Pascal de Bruijn <p.debruijn@unilogic.nl>
Tested-by: Pascal de Bruijn <p.debruijn@unilogic.nl>
Acked-by: Himanshu Madhani <himanshu.madhani@cavium.com>
Cc: Quinn Tran <quinn.tran@cavium.com>
Cc: <stable@vger.kernel.org> # 3.10+
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

drivers/scsi/qla2xxx/qla_target.h

@@ -868,6 +868,7 @@ struct qla_tgt_cmd {
 	unsigned char sense_buffer[TRANSPORT_SENSE_BUFFER];
 
 	spinlock_t cmd_lock;
+	struct completion write_pending_abort_comp;
 	/* to save extra sess dereferences */
 	unsigned int conf_compl_supported:1;
 	unsigned int sg_mapped:1;