[SCSI] qla4xxx: Clear DDB index map upon connection close failure

Issue:
qla4xxx Unable to clear DDB indices when logout fails due to
failure of connection close mbox command.

Root cause:
If login to session fail, iscsiadm make call to destroy_session.
qla4xxx driver does not free ddb index map before free_ddb()

Fix:
Clear DDB Index map before free_ddb in "destroy_session"
in case of connection close mailbox command failure with 4005h.

Signed-off-by: Nilesh Javali <nilesh.javali@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>