Add a playbook that tests collectd 6 vs collectd5

Add a playbook that tests collectd 6 vs collectd5

The playbook will:

* build collectd-6, collectd-latest and flask app
  containers
* generate a set of collectd configs
* launch the collectd-6, collectd-latest with the generated configs
* run the flask app which has a http_server that receives metrics from
  collectd v5 and collectd v6
* display the received metrics from both versions of collectd
  Collectd v5 shows PUTVAL
  Collectd v6 shows PUTMETRIC

The playbook takes the following parameters:
* PR (optional)
  The PRID for an upstream collectd pull request that will be
  passed to the collectd 6 container build

* plugin (optional)
  The name of the plugin that is bneing ported
  This will filter the received metrics to show the value passed.

Additional updates to existing roles include:
* run_collectd
  parameterises the collectd container name so that the role can be reused for
  launching multiple collectd containers by passing distinct names.

Change-Id: Ia62196c347387d380aae69e14ed0dd8e2c76d9c9
Signed-off-by: Emma Foley <efoley@redhat.com>