Sync with global requirements

There are still some problems with requirements updates proposal script,
so, syncing requirements manually.

* bump pbr to >=0.6,<1.0
* bump python-keystoneclient to >=0.5.0

Change-Id: Id87a67c2d1d96da68f3eb12db1c2a310f0cad9b9
Merge "Sync with global requirements"