Update min tox version to 2.0
Update min tox version to 2.0

The commands used by constraints need at least tox 2.0.  Update to
reflect reality, which should help with local running of constraints
targets.

Change-Id: Ia50a573ea990301c043b14faa33fe62e672900ff

openstack/puppet-pacemaker,openstack/puppet-pacemaker,openstack/puppet-pacemaker,openstack/puppet-pacemaker