Update to use the stable ppa for datadog.

Remove the old repository.

Explicitly control the version of Datadog.

playbooks/roles/datadog/defaults/main.yml

 ---
 DATADOG_API_KEY: "SPECIFY_KEY_HERE"
 
+datadog_agent_version: '1:5.0.4-516'
+
 datadog_apt_key: "0x226AE980C7A7DA52"
 datadog_debian_pkgs:
   - apparmor-utils

playbooks/roles/datadog/tasks/main.yml

@@ -26,13 +26,18 @@
   tags:
     - datadog
 
+- name: remove unstable apt repository
+  apt_repository_1.8: repo='deb http://apt.datadoghq.com/ unstable main' validate_certs=no state=absent
+  tags:
+    - datadog
+
 - name: install apt repository
-  apt_repository_1.8: repo='deb http://apt.datadoghq.com/ unstable main' update_cache=yes validate_certs=no
+  apt_repository_1.8: repo='deb http://apt.datadoghq.com/ stable main' update_cache=yes validate_certs=no
   tags:
     - datadog
 
 - name: install datadog agent
-  apt: pkg="datadog-agent"
+  apt: pkg="datadog-agent={{ datadog_agent_version }}"
   tags:
     - datadog