[SCSI] qla4xxx: Fixed session destroy issue on link up-down.

During link down, iscsid tries to do re-login to failed session. In case of
link down-up-down, LLD was sending connection login failed event to iscsid,
which is destroying the session, instead we have to continue re-login by
sending connection err event.

JIRA Key: UPSISCSI-134

Signed-off-by: Manish Rangankar <manish.rangankar@qlogic.com>
Signed-off-by: Vikas Chaudhary <vikas.chaudhary@qlogic.com>
Reviewed-by: Mike Christie <michaelc@cs.wisc.edu>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>