[Fix gate]Update test requirement
[Fix gate]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: Iaf1274dff9e41e562e5180ffdd8f526dca3243d3

openstack/python-zaqarclient