OpenStack's Python release jobs don't run tox, and don't install the
projects being packaged, not even in the branch tarball variants
these days. Remove the bindep, ensure-tox and collect-tox-logs roles
from pti-python-tarball and python-branch-tarball playbooks so that
the jobs using them can be more portable between distro versions
with less work. This should also make the jobs considerably faster.
Change-Id: Icc30a79f770ed78674354f6226d28907bab7eb1d
a4c873b51a