Merge "Enable HAProxy Prometheus metrics endpoint"

ansible/inventory/all-in-one

ansible/inventory/multinode

ansible/roles/loadbalancer/tasks/upgrade.yml

.../roles/loadbalancer/templates/haproxy/haproxy_main.cfg.j2

ansible/roles/prometheus/defaults/main.yml

ansible/roles/prometheus/handlers/main.yml

ansible/roles/prometheus/tasks/precheck.yml

.../prometheus/templates/prometheus-haproxy-exporter.json.j2

ansible/roles/prometheus/templates/prometheus.yml.j2

ansible/site.yml

etc/kolla/globals.yml

...otes/notes/haproxy-metrics-endpoint-d62c0f34e29a10b2.yaml

specs/prometheus.rst

tests/templates/inventory.j2