Fix bug for neutron network-name

There may be cases when the network-name is not updated correctly
due to the requested networks not being owned by the tenant.

In the case when there is no matched network we use the details
from the used port.

A failed deletion of a port will raise an exception. If the
port is not found no exception will be raised.

Co-authored-by: Evgeny Fedoruk <EvgenyF@Radware.com>

Closes-Bug: #1246258
(cherry picked from commit b12da559b6a40fba4e4431d74372b5e350047525)

Conflicts:
	nova/tests/network/test_neutronv2.py

Change-Id: Ie28e88ec9a9c7a180410ae5e57f84b1f653bbffc
Merge "Fix bug for neutron network-name" into stable/havana