Ignore xqueue user creation error

* xqueue user creation fails mysteriously sometimes. We don't actually
  care if the user creation works because most of the time, the user has
  already been created. So, ignore these errors.

playbooks/roles/xqueue/tasks/main.yml

@@ -30,6 +30,7 @@
     shell=/bin/bash
     home={{ xqueue_user_home }}
     createhome=yes
+  ignore_errors: true
   tags:
   - forum
   - update