Fix secondary version detection for python and revert back to using /tmp for current working dir during virtualenv install.

The secondary version detection for Python uses the python -V command, unfortunately the output is to stderr instead of stdout and has to be redirected since Puppet does not parse stderr.

If virtualenv target directory does not exist during installation the Puppet script will fail since the current working directory needs to exist before running Exec, this reverts the current working directory back to /tmp.s