This change duplicates the ideas started in with the placement-perfload
job and builds on it to create a set of nested trees that can be
exercised.
In placement-perfload, placeload is used to create the providers. This
proves to be cumbersome for nested topologies so this change starts
a new model: Using parallel [1] plus instrumented gabbi to create
nested topologies in a declarative fashion.
gate/perfload-server.sh sets up placement db and starts a uwsgi server.
gate/perfload-nested-loader.sh is called in the playbook to cause gabbi
to create the nested topology described in
gate/gabbits/nested-perfload.yaml. That topology is intentionally very
naive right now but should be made more realisitc as we continue to
develop nested features.
There's some duplication between perfload.yaml and
nested-perfload.yaml that will be cleared up in a followup.
[1] https://www.gnu.org/software/parallel/ (although the version on
ubuntu is a non-GPL clone)
Story: 2005443
Task: 30487
Change-Id: I617161fde5b844d7f52dc766f85c1b9f1b139e4a
8723bd7772