This commit updates os_nova to use tempest for functional testing of
nova. For this to work on openstack-infra instances we have to drop
all existing iptables rules using iptables-clear.sh. This commit also
updates the netmask used across containers as we currently have a mix
of /22 and /24.
Note that I couldn't get the vxlan traffic to work over
10.100.100.0/22, so I created br-vxlan and wired separate container
interfaces into that.
Change-Id: I33378e6275b70152d45357ac1ceb200ea4d5daf0