Enable super-on-old-class pylint check
Enable super-on-old-class pylint check

.. and disable the check locally for two midonet and Ryu classes that
fail since the midonet/ryu libraries are unavailable in our toxenv.

Change-Id: Idca46f853e6a116e8b2c246b4c6cae159894f887
Cherry-picked from openstack/neutron

Tehsmash/networking-cisco,hareeshpc/networking-cisco,Gitweijie/first_project,CiscoSystems/networking-cisco,noironetworks/networking-cisco,openstack/networking-cisco,noironetworks/networking-cisco,cisco-openstack/networking-cisco,openstack/networking-cisco,cisco-openstack/networking-cisco,hareeshpc/networking-cisco,Tehsmash/networking-cisco,CiscoSystems/networking-cisco,Gitweijie/first_project