Jenkins-datadog configuration

When using datadog on Jenkins, it should include datadog's provided Jenkins capabilities.

Includes jenkins-specific datadog concfiguration

playbooks/roles/jenkins_master/meta/main.yml

 ---
 dependencies:
   - common
+  - role: datadog
+    COMMON_ENABLE_DATADOG: True

playbooks/roles/jenkins_master/tasks/datadog.yml

+- name: enable jenkins datadog
+  shell: cp /etc/dd-agent/conf.d/jenkins.yaml.example /etc/dd-agent/conf.d/jenkins.yaml creates=/etc/dd-agent/conf.d/jenkins.yaml
+  notify: restart the datadog service

playbooks/roles/jenkins_master/tasks/main.yml

@@ -126,3 +126,5 @@
     dest=/etc/nginx/sites-enabled/jenkins
     state=link
   notify: start nginx
+
+- include: datadog.yml tags=datadog