Upon kuryr-controller restarted the information about the pre-created
ports is lost and therefore the ports remain created on the neutron
side. In order to avoid having ports leftovers, this patch ensures
they are cleaned up for the generic neutron case and they are
recovered and returned to the corresponding pools for the nested one.
Partially Implements blueprint ports-pool
Change-Id: Ic1f18b483130b753b160cf38843a610537b18466
330985932e