Replace hard-coded setup version setting

The pbr library is used to generate version numbers for Barbican, and
should typically do so by forming the version using the latest tag
(such as '2014.2.b2') as a base version, and then appending git commit
info if after the tag. However, if setup.cfg has a 'version' property
set, this overrides the base version essentially 'hard coding' it. This
CR removes that override and instead lets the versionbuild.py script,
used during deployment processing, generate this version override based
on the current PBR generated version with a timestamp injected into it.

Closes-Bug: #1349238
Change-Id: I32cf9b32265569c1e2ae182efa32a0d1449de15c
Merge "Replace hard-coded setup version setting"