paunch is a library and utility which is now in OpenStack
under the TripleO umbrella. It contains the logic currently in the
docker-cmd hook exposed as a python library and command utility.
This change switches the docker-cmd hook to paunch.
Asserting --label arguments has been split out from the other docker
run arguments so that paunch can add new --label arguments in future
releases without breaking these tests.
paunch-1.1.0 has just been release which contains new idempotency
behaviour, so the tests have been modified to work with the new docker
command behaviour that idempotency requires.
Change-Id: I884c38ade06ab0e01432837c43f29b123e65fa3c
33241a84c1