Opensearch datasource plug-in index pattern is misconfigured

[Dawud]

In ansible/roles/grafana/defaults/main.yml we have specified a YYYY.MM.DD pattern for the index (flog-YYYY.MM.DD):

```
grafana_data_sources:
<...Removed irrelevant code...>
  opensearch:
    enabled: "{{ enable_opensearch | bool }}"
    data:
      name: "opensearch"
      type: "grafana-opensearch-datasource"
      access: "proxy"
      url: "{{ opensearch_internal_endpoint }}"
      jsonData:
        flavor: "elasticsearch"
        database: "[flog-]YYYY.MM.DD"
        version: "7.0.0"
        timeField: "@timestamp"

However this does not work out of the box. When you go to the datasource section of Grafana and click "Save and test" with these defaults, it fails with `OpenSearch error: no such index [[flog-]YYYY.MM.DD]`

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: stable/yoga
Review: https://review.opendev.org/c/openstack/kolla-ansible/+/898736

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.opendev.org/c/openstack/kolla-ansible/+/913320

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/c/openstack/kolla-ansible/+/913320
Committed: https://opendev.org/openstack/kolla-ansible/commit/9afc9da22621cc808287874915ab3c1305592d15
Submitter: "Zuul (22348)"
Branch: master

commit 9afc9da22621cc808287874915ab3c1305592d15
Author: Dawud <email address hidden>
Date: Fri Mar 15 10:49:51 2024 +0000

    Update Grafana OpenSearch datasource configuration

    Updates the Grafana OpenSearch datasource configuration to use values
    for OpenSearch that work out of the box.

    Closes-Bug: #2039500
    Change-Id: Id9c7e59e6ae1dd98176c68b14a2aff1985306751

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: stable/2023.2
Review: https://review.opendev.org/c/openstack/kolla-ansible/+/917097