Use configured values instead of default value
Use configured values instead of default value

Variables PUBLIC_INTERFACE_DEFAULT and GUEST_INTERFACE_DEFAULT
are only use to provide default value, deployment script should
not use such values directly

Closes-Bug: #1566768

Change-Id: Ib543b416df861086fa2edbe7df769b224d0b0add

group-policy/devstack,bswartz/devstack,bigswitch/devstack,noironetworks/devstack,richliu/devstack,group-policy/devstack,nawawi/openstack,Mahito/devstack,richliu/devstack,nawawi/openstack,dtroyer/devstack,noironetworks/devstack,openstack-dev/devstack,bswartz/devstack,bigswitch/devstack,openstack-dev/devstack,dtroyer/devstack,Mahito/devstack