Update health policy example

[Duc Truong]

The health policy example files (https://github.com/openstack/senlin/blob/master/examples/policies/health_policy_poll_url.yaml) are outdated.

The health policy schema now uses detection_modes. E.g.

type: senlin.policy.health
version: 1.0
description: A policy for maintaining node health from a cluster.
properties:
  detection:
    interval: 60
    node_update_timeout: 240
    detection_modes:
      - type: NODE_STATUS_POLL_URL
        options:
          poll_url: "http://127.0.0.1:5000"
          poll_url_retry_limit: 3
          poll_url_retry_interval: 2
      - type: NODE_STATUS_POLLING
  recovery:
    actions:
      - name: RECREATE
    node_delete_timeout: 90
    node_force_recreate: True

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/668246
Committed: https://git.openstack.org/cgit/openstack/senlin/commit/?id=ebefa20ca207575d9c7045d2ed257a4287d9b79b
Submitter: Zuul
Branch: master

commit ebefa20ca207575d9c7045d2ed257a4287d9b79b
Author: Duc Truong <email address hidden>
Date: Fri Jun 28 20:33:04 2019 +0000

    Update docs and examples for health policy v1.1

    The documentation and example health policies need to be updated to
    reflect health policy v1.1 schema changes.

    Change-Id: Ie447397b001fba9798025370cdb0087e679fdfe4
    Closes-Bug: #1834516

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/senlin 8.0.0.0rc1 release candidate.