Make packaging dep explicit

A couple sanity tests require the packaging module.  The azure tests are
dragging it in but list it explicitly in sanity so we don't run into
problems if those are ever split up

test/runner/requirements/sanity.txt

@@ -1,6 +1,7 @@
 cryptography
 jinja2
 mock
+packaging  # needed for update-bundled and changelog
 pycodestyle
 pylint ; python_version >= '3.5' # pylint 2.0.0 and later require python 3+
 pytest