Deprecated tox -downloadcache option removed
Deprecated tox -downloadcache option removed

Caching is enabled by default from pip version 6.0

More info:
https://testrun.org/tox/latest/config.html#confval-downloadcache=path
https://pip.pypa.io/en/stable/reference/pip_install/#caching

Change-Id: I1f758ea8dbac08cef1fa5fc34c0fd21d55a71385

openstack/taskflow,jimbobhickville/taskflow,jimbobhickville/taskflow,openstack/taskflow