Add 'virtualenv' to setup_tempest role
Add 'virtualenv' to setup_tempest role

virtualenv is needed to setupthe virtual environment, when we are
installing the packages and running tempest.

Without it installed, you will recieve the follwoing error:
"which: no virtualenv in (/usr/local/bin:/usr/bin)\nPlease
install 'python-virtualenv'".

Change-Id: Id50c6e9c0eebf8d8351ba17e0f8d79812262f811

redhat-openstack/octario,redhat-openstack/octario