greenlet version inconsistency
greenlet version inconsistency

Fixes Bug #917003

The latest version of greenlet is installed in install_venv.py while
the version required is set to 0.3.1 in pip-requires.

Change-Id: I145deb46a8edc41e87634dc5ca839baf5acd8065

zancas/hacking,emonty/oslo-hacking,emonty/oslo-hacking,zancas/hacking,hyakuhei/cleantox,openstack-dev/hacking,hyakuhei/cleantox,openstack-dev/hacking