The previous version just created a network name space which does
not allow us to also test additional namespaces, e.g. for unix
domain sockets.
This commit uses runc to create a fully namespaced container to
run a test in. It creates a container, configures the network
interfaces in the new network namespace before starting the
container.
A OCI config.json template is used and then customised for a
given test based on command line arguments.
Finally, instead of iperf, we use the socket stress test from
https://github.com/linuxkit/virtsock as it provides finer-grained
control over the traffic patterns (e.g. long lived vs lots of
short lived connections).
Signed-off-by: Rolf Neugebauer <rolf.neugebauer@docker.com>
