FakeNotifier class 'topic' argument change to 'topics'.
FakeNotifier class 'topic' argument change to 'topics'.

Oslo.messaging commit: 2d53db6c51c2ac2ccddda210906c1e6418557470
changed topic to be a list.

Change-Id: I24032c91d2f01687009d6e32a972d34b248962c4
Closes-Bug: #1736220

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