put the dependency on maas in the meta data

Change-Id: Icefbe3744e9f87fda13e70e8730c179df3e295d3
diff --git a/roles/head-node/meta/main.yml b/roles/head-node/meta/main.yml
index 69caefd..97b4caa 100644
--- a/roles/head-node/meta/main.yml
+++ b/roles/head-node/meta/main.yml
@@ -12,4 +12,5 @@
   galaxy_tags:
     - cord
 dependencies:
+  - { role : maas }
   - { role : ansible }