Basically revert my previous commits as the policy templates are
generated during the build. The only thing that we were copying out from
the tarballs was the policy templates documentation, but that one is
generated as well so use that one and remove the policy_templates zip
file from sources
- Download the policy templates per release channel
- Only run the nacl_versions when not running on python 2.6 as the
toolchain_build modules are not python 2.6 compatible
