Parallelize docker-puppet.py
Parallelize docker-puppet.py

Use a pool of worker processes to run the puppet modules so they
can all be done in parallel.  Defaults to cpu count processes.

Change-Id: I083d302b8cf6538569e4d165221c21df152266bc

dprince/tripleo-heat-templates,dprince/tripleo-heat-templates,openstack/tripleo-heat-templates,openstack/tripleo-heat-templates