The old novaclient.v2.server.Server.interface_attach() method is
replaced with proxy.create_server_interface().
In swargs, 'net_id' and 'port_id' are mutual-exclusive, if one of
them is given with value, the other one cannot be None, as the
API would responde with 400 (None is not string).
In unit test, temporary method 'setup_sdk_servers_mock' is added,
because other tests are still using the old 'setup_servers_mock'.
Functional tests are added. Releasenote is generated.
Change-Id: I9899f0509febc5143560a1859ae6344d0a6d1427
2183a61147