add support for configuring trace agent

With 5.11.0, there are additional sections in datadog.conf observed
by the trace agent.

But changing the semantics of `datadog_config` will break backwards
compatibility with existing role users expecting that dictionary
to populate the [Main] section.

Instead, we add another nested dictionary to support extra
sections.

Author: pmbauer

README.md

@@ -18,7 +18,8 @@ Role Variables
 
 - `datadog_api_key` - Your Datadog API key.
 - `datadog_checks` - YAML configuration for agent checks to drop into `/etc/dd-agent/conf.d`.
-- `datadog_config` - Settings to place in `/etc/dd-agent/datadog.conf`.
+- `datadog_config` - Settings to place in `/etc/dd-agent/datadog.conf` ini that go under `[Main]`.
+- `datadog_config_ex` - extra ini sections to go in `/etc/dd-agent/datadog.conf`.
 - `datadog_process_checks` - Array of process checks and options (DEPRECATED: use `process` under
 `datadog_checks` instead)
 - `datadog_apt_repo` - Override default Datadog `apt` repository
@@ -40,6 +41,11 @@ Example Playbooks
     datadog_config:
       tags: "mytag0, mytag1"
       log_level: INFO
+    datadog_config_ex:
+      trace.config:
+        env: dev
+      trace.concentrator:
+	extra_aggregators: version
     datadog_checks:
       process:
         init_config:

templates/datadog.conf.j2

@@ -16,3 +16,10 @@
 {% if datadog_config -%}
   {{ datadog_config | to_nice_yaml }}
 {% endif %}
+
+{% if datadog_config_ex is defined -%}
+{% for key, value in datadog_config_ex.iteritems() %}
+[{{ key }}]
+{{ value | to_nice_yaml }}
+{% endfor %}
+{% endif %}