Ensure latest setuptools is present.

Upgrading to the latest setuptools in isolation works fine, but
if the upgrade is caused by a dependency and the distribute/setuptools
upgrade happens in a bad sequence, one can wind up with a broken
setuptools environment.

Change-Id: I3d55232ac9377156e405e16dac2f07cfcaa70ff5
Merge "Ensure latest setuptools is present."