Add the ability to pick preseed based on MAC address

Change-Id: Idfa5085389d227c8f96fec42f94b069424085ba5
diff --git a/molecule/default/prepare.yml b/molecule/default/prepare.yml
index 387f291..00ea0fe 100644
--- a/molecule/default/prepare.yml
+++ b/molecule/default/prepare.yml
@@ -8,8 +8,18 @@
 - name: Prepare for pxeboot role
   hosts: all
 
+  vars:
+    acme_username: "www-data"  # make independent of the acme role
+    vhosts:
+      - name: "boot.example.com"
+        default_server: true
+        autoindex: true
+
   pre_tasks:
 
     - name: update apt cache
       apt:
         update_cache: true
+
+  roles:
+    - nginx