Documenting subnet_allocation extension
Documenting subnet_allocation extension

Closes-Bug: #1733395

Change-Id: I666ad54e3fa179c19c4b9a255d088bca0651c66d
Signed-off-by: Michal Kelner Mishali <5c58114e82cdbe8f8b208a55e01273a9a20ee696@vmware.com>

openstack/neutron-lib,openstack/neutron-lib,openstack/neutron-lib,openstack/neutron-lib