Currently we generate multiple fluentd configuration files for inputs,
filters, formatters and outputs.
These are then included from the main td-agent.conf configuration file.
With a large number of hosts, this can take a long time to template.

Benchmarking of templating is available at [1].

This change switches to a single fluentd configuration file, with the
include done locally. For the default template files included with Kolla
Ansible we use Jinja includes, but this does not work with templates in
a different directory. We therefore use the Ansible template lookup
plugin, which has a slightly higher overhead than a jinja include, but
far lower than generating multiple templates. This should drastically
improve the performance of this task.

[1] https://github.com/stackhpc/ansible-scaling/blob/master/doc/template.md

Partially-Implements: blueprint performance-improvements

Change-Id: Ia8623be0aa861fea3e54d2c9e1c971dfd8e3afa9