add dynamic ansible inventory script

Change-Id: I3e8ba79d0d6ec8e66e5118638ec9325ee78d50ef
diff --git a/roles/head-node/vars/main.yml b/roles/head-node/vars/main.yml
index e97daf1..0093928 100644
--- a/roles/head-node/vars/main.yml
+++ b/roles/head-node/vars/main.yml
@@ -7,3 +7,6 @@
     location: "{{ prov_location | default('http://gerrit.opencord.org/maas') }}"
     role_path: "{{ prov_role_path | default('roles') }}"
     role: "{{ prov_role | default('compute-node') }}"
+
+maas:
+    user: "{{ maas_user | default('cord') }}"