This patch adds a tempest scenario test for active/standby topology.
This scenario takes a similar approach to scenario proposed in Change-Id
Ibcd5552a67cea650edc72bfaa986357267ca2407 with the difference that it
does not rely on amphora stats API. Instead, it uses iptables to log VIP
traffic and make assertions based on logging.
Co-Authored-By: Michael Johnson <email@example.com>