revert "support setup.py install with git archive tarballs" commit

revert the following commit because it has a side effect
to change pbr's version to ryu's version. (eg. 3.1)
it doesn't work with the recent version of olso.config
which requires pbr < 1.0.

|commit 55aa47489306ebb3bfa3307e3fa5a332007a58ed
|Author: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
|Date:   Fri Aug 2 14:33:40 2013 +0900
|
|    support setup.py install with git archive tarballs
|
|    Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
set PBR_VERSION in a different place