scsi: be2iscsi: Set and return right iface v4/v6 states

ipv4_iface and ipv6_iface fields need to be set to NULL when destroyed.
Before creation these are checked. Use these to report correct states.

Signed-off-by: Jitendra Bhivare <jitendra.bhivare@broadcom.com>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>