charms.openstack does not provide a way for charm author to provide multiple templates with same basename

[Frode Nordahl]

The ``render`` method of the ``charmhelpers.contrib.openstack.OSConfigRenderer`` class provides a way for charm authors to provide templates with equal basenames but different absolute paths. This is also useful for templates that have an ambiguous basename.

The way this works is that if a template is not found while rendering the render loop will retry with a source path built from the absolute path of the target configuration file with path separators replaced by underscores.

We should implement this for ``charms.openstack``.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.opendev.org/719920

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/719920
Committed: https://git.openstack.org/cgit/openstack/charms.openstack/commit/?id=f9bd43ff5ddec906365dbc8a898443b91a19d554
Submitter: Zuul
Branch: master

commit f9bd43ff5ddec906365dbc8a898443b91a19d554
Author: Frode Nordahl <email address hidden>
Date: Tue Apr 14 13:16:27 2020 +0200

    Support charms providing templates with same basename

    Replicate functionaltiy of ``charmhelpers.contrib.openstack``
    where template files named after the absolute path of target
    with path separators repalced by underscores can be used.

    This convention is useful when charm author need to provide
    templates with ambiguous basename.

    Change-Id: I534fe52f38df7d1e409246115836223e90f080bc
    Closes-Bug: #1872689