[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: I5a3edd93326b4b926b99fa5f5aa60b4213267e01

openstack/designate-dashboard,openstack/designate-dashboard,openstack/designate-dashboard