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: Ie3de2504fe08f751dbf3f06e4973716a51d7e25b
Merge "Sync install_venv_common from oslo"