scsi: qla2xxx: Remove unintended flag clearing

FCF_ASYNC_SENT flag is used in session management. This flag is cleared in
task management path by accident.  Remove unintended flag clearing.

Fixes: 388a4995 ("scsi: qla2xxx: Fix panic from use after free in qla2x00_async_tm_cmd")
Cc: stable@vger.kernel.org
Signed-off-by: Quinn Tran <qutran@marvell.com>
Signed-off-by: Nilesh Javali <njavali@marvell.com>
Reviewed-by: Himanshu Madhani <himanshu.madhani@oracle.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>