[nullmailer] Define allmailfrom to always send mails as root

Signed-off-by: Yohann D'ANELLO <ynerant@crans.org>

group_vars/all/nullmailer.yml

@@ -3,3 +3,4 @@ glob_nullmailer:
   root: root@crans.org
   smtp_server: smtp.adm.crans.org
   defaulthost: crans.org
+  allmailfrom: root@crans.org

roles/nullmailer/tasks/main.yml

@@ -26,3 +26,9 @@
     content: "{{ nullmailer.defaulthost }}\n"
     dest: /etc/nullmailer/defaulthost
     mode: 0644
+
+- name: Set nullmailer allmailfrom
+  copy:
+    content: "{{ nullmailer.allmailfrom }}\n"
+    dest: /etc/nullmailer/allmailfrom
+    mode: 0644