Remove unused imports
Remove unused imports

Remove unused imports in tools/install_venv.py

Change-Id: Ia2fbb4ece5c8bcdee96503f0f853f826ae4f3dfa
Closes-Bug: #1265267

citrix-openstack-build/neutron-vpnaas,openstack/neutron-vpnaas,dougwig/x-neutron-vpnaas,openstack/neutron-vpnaas