Mask environment configuration with no_log

Environment files are frequently used to inject sensitive values to daemons. This change enables the no_log flag on this task.

Alternatively, we could have two tasks that do the same thing and require users to opt out/in like such:

```yaml
prometheus_my_exporter_env_vars:
   foo: 'not a secret, i like my diffs'
prometheus_my_exporter_env_insensitive: true
```

Author: dekimsey

tasks/_service.yml

@@ -23,6 +23,7 @@
   notify:
     - Restart Prometheus service
   when: prometheus_software_env_vars is defined and prometheus_software_env_vars
+  no_log: True
 
 - name: Include task to setup {{ prometheus_software_name_version }} {{ ansible_service_mgr }} service
   include_tasks: '_service_mgr_{{ ansible_service_mgr | regex_replace("^(openrc|upstart)$", "init") }}.yml'