Require pbr 0.5.16 or newer
Require pbr 0.5.16 or newer

Use a version of pbr greater then 0.5.15. Earlier versions have problems
when alpha tarballs are used as dependencies.

Fixes bug 1191155

Change-Id: I889358ae746761b282c5933c53bce10017be4c57

openstack/networking-mlnx,stackforge/networking-mlnx,moshele/networking-mlnx,moshele/networking-mlnx-master,openstack/networking-mlnx,stackforge/networking-mlnx