[SCSI] iscsi class: fix iscsi conn attr counter

There are 13 iscsi conn attrs, but since the IF/OF markers were not being
used we did not notice that we forgot to increment the ISCSI_CONN_ATTRS
counter.

Signed-off-by: Mike Christie <michaelc@cs.wisc.edu>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>