Fix for OPENSTACK-783
Fix for OPENSTACK-783

It should not return the ATTR_NOT_SPECIFIED object in the response.
It is safe to set the rate to None here, as a floatingip not connected
to a port can't have any rate limit anyway.

Change-Id: Iad47500894903c85364e171938b3773bb805ff41
Closes-Bug: OPENSTACK-783

naveensan1/nuage-openstack-neutron,naveensan1/nuage-openstack-neutron,nuagenetworks/nuage-openstack-neutron,nuagenetworks/nuage-openstack-neutron