utils: fix python install for rule/ subdirectory

For reasons that are unclear, python's setuptools doesn't install
recursively from a directory, meaning that on make install, the new
Rules/Ruleset classes were not being installed. This patch causes
the rule subdirectory to be included.

Bug: https://bugs.launchpad.net/bugs/1407437

Signed-off-by: Steve Beattie <steve@nxnw.org>
Acked-by: Tyler Hicks <tyhicks@canonical.com>