venv: update distribute as well as pip
venv: update distribute as well as pip

When you create a virtualenv, pip and setuptools/distribute is
installed.

When we later run install_venv.py to update the venv, we should
be sure to grab the latest versions of pip and distribute otherwise
issues like this one are masked:

  http://code.google.com/p/sqlalchemy-migrate/issues/detail?id=131

Change-Id: Id206be478ea6c5216dcee6f2f58dc91858c843f5

openstack-dev/hacking,emonty/oslo-hacking,hyakuhei/cleantox,emonty/oslo-hacking,zancas/hacking,hyakuhei/cleantox,openstack-dev/hacking,zancas/hacking