Add collectd-libpod-stats to image

This patch adds the installation of collectd-libpod-stats as part of the
collectd image. The package is available in the centos-opstools repo.

Collectd-libpod-stats monitors resource usage of running containers on a
host, specifically those managed by the libpod library.

Adapted for Train to affect only CentOS/RHEL 8 image.

Upstream: https://github.com/pleimer/collectd-libpod-stats

Change-Id: I12efbaae9c0795f29c2f68158127509fd1b543b0
Signed-off-by: pleimer <pfbleimer@gmail.com>
(cherry picked from commit 094a49d41d)
(cherry picked from commit ce7cd47844)

docker/collectd/Dockerfile.j2

@@ -55,6 +55,7 @@ LABEL maintainer="{{ maintainer }}" name="{{ image_name }}" build-date="{{ build
   {% if distro_python_version.startswith('3') %}
   {% set collectd_packages = collectd_packages + [
       'collectd-dpdk_telemetry',
+      'collectd-libpod-stats',
       'collectd-logparser',
       'python3-sqlalchemy-collectd'
   ] %}