Update test requirement
Update test requirement

Since pbr already landed and the old version of hacking seems not
work very well with pbr>=2, we should update it to match global
requirement.
Partial-Bug: #1668848

Change-Id: I0bf52b0ad447d32f672543fa46f24951b0d786fb

openstack/ironic-ui,openstack/ironic-ui,openstack/ironic-ui,openstack/ironic-ui