Add API test to ensure IPs can be added by subnet
Add API test to ensure IPs can be added by subnet

A user should be able to request additional fixed IPs
from the same subnet they already have an IP from.
This prevents a regression from that behavior.

Related-Bug: #1623800
Change-Id: I1867963e027f8d240580ada89b540443f74ed684

cloudbase/neutron,sebrandon1/neutron,mahak/neutron,mahak/neutron,openstack/neutron,mahak/neutron,huntxu/neutron,sebrandon1/neutron,openstack/neutron,openstack/neutron,eayunstack/neutron,cloudbase/neutron,huntxu/neutron,noironetworks/neutron,eayunstack/neutron,noironetworks/neutron