Work around Kubernetes rejecting underscores in configmap paths

1) ConfigMaps can be loaded from a file with underscores in the file name, as long as you provide a non-underscore filename: `kubectl create configmap horizon-configmap --from-file=/etc/kolla/horizon/horizon.conf --from-file=/etc/kolla/horizon/config.json --from-file=local-settings=/etc/kolla/horizon/local_settings`

2) ConfigMaps can be set to mount a file to a specific path:
        items:
        - key: local-settings
          path: local_settings