Replace the api_key line if it already exists.

playbooks/roles/datadog/tasks/main.yml

@@ -56,9 +56,9 @@
 - name: datadog | update api-key
   lineinfile: 
     dest="/etc/dd-agent/datadog.conf" 
-    "regexp=^api_key:$" 
-    "line=api_key:{{ common_datadog_api_key }}"
+    "regexp=^api_key:.*"
+    "line=api_key:{{ common_dd_api_key }}"
   notify:
     - datadog | restart the datadog service
   tags:
-    - datadog
\ No newline at end of file
+    - datadog