Sync install_venv_common from oslo

The current version of install_venv_common uses the --distribute flag
in its creation of the virtualenv. This causes some upgrade problems
with the new versions of distribute and setuptools. The solution to
those problems is to get off of the distribute bandwagon.

Change-Id: I5efe196c46b12d88c853f8362ebcbf0cc6f1573d