scsi: be2iscsi: Fix to use correct configuration values

Following configuration is created with what driver exports:
iface.vlan_id = 65535
iface.vlan_priority = 255
iface.vlan_state = <empty>

vlan_state is empty as iscsiadm doesn't process "Disabled".
When applying this configuration, iscsiadm checks for if vlan_state is
"disable" if not it enables with value in vlan_id. 65535 not being valid
value, 0 is applied.

Use "enable" or "disable" for ISCSI_NET_PARAM.

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>