scsi: tcm_qla2xxx: Do not allow aborted cmd to advance.

In case of hardware queue full, commands can loop between
TCM stack and tcm_qla2xx shim layers for retry. While command
is waiting for retry, task mgmt can get ahead and abort the
cmmand that encountered queue full condition. Fix this by
dropping the command, if task mgmt has already started the
command free process.

Acked-by: Nicholas Bellinger <nab@linux-iscsi.org>
Signed-off-by: Quinn Tran <quinn.tran@cavium.com>
Signed-off-by: Himanshu Madhani <himanshu.madhani@cavium.com>
Reviewed-by: Bart Van Assche <Bart.VanAssche@sandisk.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>