Use responseChoice to delete existing public subnet
Use responseChoice to delete existing public subnet

The existing public subnet in a devstack deployment is
made by an openstack deployment and will have an external
id. responseChoice=1 is needed to delete this resource.

Change-Id: I950e73f9ad037624b9bfca3f75e817b7e6b912c4

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