Fix usage of wrong venv for tempest_conf
Fix usage of wrong venv for tempest_conf

Wrong virtual environment for discover-tempest-config is sourced
which leads to a 'command not found' error.

Change-Id: Ib25a783b82450673ccf81022891535f733b99ca4

okolisny/InfraRed,okolisny/InfraRed,redhat-openstack/infrared,redhat-openstack/infrared,okolisny/InfraRed,redhat-openstack/infrared