Currently we deploy the openstacksdk config into ~nodepool/.config on
the container, and then map this directory back to /etc/openstack in
the docker-compose. The config-file still hard-codes the
limestone.pem file to ~nodepool/.config.
Switch the nodepool-builder_opendev group to install to
/etc/openstack, and update the nodepool config file template to use
the configured directory for the .pem path.
Also update the testing paths.
Story: #2007407
Task: #39015
Change-Id: I9ca77927046e2b2e3cee9a642d0bc566e3871515
b967495dc3