Launches an interactive ipython environment, attached to Infix nodes.
This can be used as a playground for developing tests, testing out
NETCONF operations, etc.
When running in the cloud, without KVM emulation, together with many
other tenants, it can take a very long time to boot the instances.
Therefore, add a meta test that will wait for all devices in the
physical topology to come up before exiting. This means that the
actual test cases that follow can assume that devices will answer
NETCONF requests.
