Fix fwaas v1 configuration doc
Fix fwaas v1 configuration doc

Modify the fwaas v1 config about  driver

Change-Id: Id6821174a15838713435a499a258f6d37a9cad2a
Closes-Bug: #1777547

openstack/neutron,huntxu/neutron,openstack/neutron,mahak/neutron,openstack/neutron,mahak/neutron,mahak/neutron,huntxu/neutron,noironetworks/neutron,noironetworks/neutron