Use MaaS node key when on_maas

Change-Id: Ie5708aac996647ee532d33a82ec5e9af468645a8
diff --git a/roles/onos-vm-install/templates/onos-setup-vars.yml.j2 b/roles/onos-vm-install/templates/onos-setup-vars.yml.j2
index cd21505..136e686 100644
--- a/roles/onos-vm-install/templates/onos-setup-vars.yml.j2
+++ b/roles/onos-vm-install/templates/onos-setup-vars.yml.j2
@@ -1,2 +1,6 @@
 ---
-
+{% if on_maas %}
+node_private_key: "{{ maas_node_key }}"
+{% else %}
+node_private_key: "~/.ssh/id_rsa"
+{% endif %}