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: I635dbf199bad59c72401a4de1de5200132746f6f

pshchelo/ironic,pshchelo/ironic,openstack/ironic,SauloAislan/ironic,NaohiroTamura/ironic,NaohiroTamura/ironic,openstack/ironic,SauloAislan/ironic