Fix API reference for os-floating-ip-dns
Fix API reference for os-floating-ip-dns

The generic warning in here about being a proxy to
neutron is incorrect since these APIs don't proxy
anything to neutron and won't work if you're using
neutron, so the warning is updated.

Part of blueprint remove-nova-network

Change-Id: I8b7638bb0835711ef174d6caf1b53e4a1808ef53

openstack/nova,gooddata/openstack-nova,gooddata/openstack-nova,mahak/nova,klmitch/nova,mikalstill/nova,rahulunair/nova,klmitch/nova,gooddata/openstack-nova,mikalstill/nova,openstack/nova,klmitch/nova,openstack/nova,rahulunair/nova,rahulunair/nova,gooddata/openstack-nova,mahak/nova,klmitch/nova,mahak/nova,mikalstill/nova