Fix unit test error
Fix unit test error

This patch fixes watcher.tests.common.test_clients.TestClients.
test_clients_ironic unit test error due to python-ironicclient 2.4.0.

Change-Id: I0aaa2047cc8fcf09dee8bc7168e35f7a58c10125

openstack/watcher,openstack/watcher,stackforge/watcher,stackforge/watcher