Set base_domain depending on vagrant

The variable cannot be set in other places, due to this one taking
precedence.

playbook.yml

@@ -3,13 +3,14 @@
   gather_facts: true
   become: true
   vars:
-    base_domain: data.coop
-    letsencrypt_email: admin@data.coop
     ldap_dn: "dc=data,dc=coop"
 
     vagrant: "{{ ansible_virtualization_role == 'guest' }}"
     letsencrypt_enabled: "{{ not vagrant }}"
 
+    base_domain: "{{ 'datacoop.devel' if vagrant else 'data.coop' }}"
+    letsencrypt_email: "admin@{{ base_domain }}"
+
     smtp_host: "postfix"
     smtp_port: "587"