RD-6082 mgmtworker rpm: include a python3.6 base venv (#3911)
RD-6082 mgmtworker rpm: include a python3.6 base venv (#3911)

This venv contains an upgraded version of pip (and also all our
cloudify-common libs) as a base for plugin installations
cloudify-cosmo/cloudify-manager,cloudify-cosmo/cloudify-manager,cloudify-cosmo/cloudify-manager