Delete Devref Enable Service for Network IP Availability
Delete Devref Enable Service for Network IP Availability

No longer need to enable extension in service_plugins.
The feature is automatically enabled after patch [1].

[1]: https://review.openstack.org/#/c/283357/

Change-Id: Ia9a36c40e33a25335a83b96adff2d675164b5d21

mahak/neutron,huntxu/neutron,klmitch/neutron,openstack/neutron,sebrandon1/neutron,openstack/neutron,eayunstack/neutron,MaximNevrov/neutron,huntxu/neutron,klmitch/neutron,mahak/neutron,cloudbase/neutron,noironetworks/neutron,noironetworks/neutron,eayunstack/neutron,bigswitch/neutron,MaximNevrov/neutron,bigswitch/neutron,mahak/neutron,sebrandon1/neutron,openstack/neutron,igor-toga/local-snat,igor-toga/local-snat,cloudbase/neutron