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: #1669276

Change-Id: I90d62333c08f4e90bccc42241fd94ad76d44bb43

ArchiFleKs/magnum,openstack/magnum,ArchiFleKs/magnum,openstack/magnum