Don't update pbr's setup.py

Due to the fact that we'd like to keep pbr's requirements in sync with
global requirements we should disable syncing of setup.py for pbr.

* existing tests fixed by adding standard setup.cfg file;
* new test case added for syncing pbr project (with pbr like setup.cfg file).

Change-Id: Ibf5fcdad118fffb4fd5dd50c5d1decfa6f9a6479
Merge "Don't update pbr's setup.py"