scsi: iscsi: iscsi_tcp: Start socket shutdown during conn stop

Make sure the conn socket shutdown starts before we start the timer to fail
commands to upper layers.

Link: https://lore.kernel.org/r/20210525181821.7617-10-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>