Look for floatingips on configured subnets
Look for floatingips on configured subnets

Define a new configuration option to list the subnets where
floatingips should be allocated, and use those subnets instead
of all of the subnets on the external network.

Change-Id: Ida1dbd9e463deb36cf3249deaad24e93f49bb575

openstack/akanda-neutron,stackforge/akanda-neutron