Conditionalize ez_setup

This makes life simpler for packagers, since most packaging tools
will ensure that the appropriate packages are available on the
system. Additionally, most packaging tools prefer not to rely on
network access (since it can mean that identical rebuilds cannot
be performed).

Built locally with 'python setup.py build' and also by applying this patch and
performing an RPM build in a network-free environment.

Built locally with 'python setup.py build' and also by applying this patch and
performing an RPM build in a network-free environment.

This review request was submitted by calling 'rbt post -g' on the version built
in that RPM without network access.