Can't have kolla config file that templates to invalid ini/yaml

[Will Szumski]

kayobe fails with:

```
TASK [kolla-openstack : Ensure extra configuration files exist (strategy: merge_yaml)] **************************************************************************************
Thursday 02 November 2023 18:42:02 +0000 (0:00:00.020) 0:00:31.182 *****
changed: [localhost] => (item={'sources': ['/home/stack/will/antelope/src/kayobe-config/etc/kayobe/kolla/config/glance/policy.yaml'], 'dest': '/home/stack/will/antelope/src/
kayobe-config/etc/kolla/config/glance/policy.yaml', 'params': []})
changed: [localhost] => (item={'sources': ['/home/stack/will/antelope/src/kayobe-config/etc/kayobe/kolla/config/grafana/provisioning.yaml'], 'dest': '/home/stack/will/antelo
pe/src/kayobe-config/etc/kolla/config/grafana/provisioning.yaml', 'params': []})
An exception occurred during task execution. To see the full traceback, use -vvv. The error was: ^
fatal: [localhost]: FAILED! =>
  msg: |-
    Unexpected failure during module execution: while scanning for the next token
    found character '%' that cannot start any token
      in "<unicode string>", line 27, column 15:
                url: {% raw %} '{{ template "__alert_s ...
                      ^
  stdout: ''
```

This is because it need the config file to parse as valid yaml/ini to merge it.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.opendev.org/c/openstack/kayobe/+/900060

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/c/openstack/kayobe/+/900060
Committed: https://opendev.org/openstack/kayobe/commit/86d9a533e80c06a3b53067f60b72f9c998713b4a
Submitter: "Zuul (22348)"
Branch: master

commit 86d9a533e80c06a3b53067f60b72f9c998713b4a
Author: Will Szumski <email address hidden>
Date: Fri Nov 3 17:42:49 2023 +0000

    Fallback to templating when only one source exists

    This is a backwards compatability improvement, since it was previously
    permitted to have a config file that templated to invalid yaml/ini.

    Change-Id: I53a0894cc64e83c7342a82ad987b7e5a4696ece2
    Closes-Bug: #2042690

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/kayobe 15.0.0.0rc1 release candidate.