scsi: iscsi: Fix completion check during abort races

We have a ref to the task being aborted, so SCp.ptr will never be NULL. We
need to use iscsi_task_is_completed to check for the completed state.

Link: https://lore.kernel.org/r/20210525181821.7617-16-michael.christie@oracle.com


Reviewed-by: Lee Duncan <lduncan@suse.com>
Signed-off-by: Mike Christie <michael.christie@oracle.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>